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Lymphocyte reactivity during spaceflight
Immunology Today January 1985 Lymphocyte reactivity during spaceflight from Augusto Cogoli a n d Alexander Tschopp Over t w e n t y years of spaceflight h a v e d e m o n s t r a t e d t h a t m a n can easily survive a n d work i n weightless conditions. However, a n u m b e r of physiological changes may affect crew performance i n space. Besides the well k n o w n disturbances of the vestibular a n d cardiovascular systems, bone demineralization, a n d decrease of erthrocyte mass, certain immunological alterations h a v e b e e n observed in space crews after flight. One of t h e m - the reduction of l y m p h o c y t e reactivity to mitogens - was the subject of o u r investigations d u r i n g the flight of Spacelab I from 28 November-8 D e c e m b e r 19~3.
Although the immunological changes noted have never had adverse consequences on the health of the astronauts,
they clearly indicate that the efficiency of the immune system is-influenced by spaceflight. Is the cause weightlessness
per se or is it stress? In our continuing investigations we are trying to answer these questions. The advent of the Space Shuttle as an operational vehicle for working in space, the proof that Spacelab is a useful tool for performing scientific experiments in several disciplines and the recent decision to build a permanently manned space station, will require a more broadly based community of scientists and technicians to spend prolonged periods of time (weeks or months) in space. This implies that the criteria for physical certification ofastronauts will be less severe so that physiological changes which have been judged to be minor or not alarming so far may not be perceived as such in the future.
Fig. 1. Incubator with lymphocyte cultures (arrow) installed in rack No. 4 of the Spacelab module during the first Spacelab mission. From left to right astronauts Robert Parker, Byron Lichtenberg, the payload specialist who operated our experiment, Owen Garriott and Ulf Merbold, (Courtesyof NASA.) © 1985, Ehevier Scmnce Publishers B.V., Amsterdam 0167
4919/85/$02.00
Immunology Today, vol. 6, No. 1, 1985
2 Table I. Effect of spaceflight on T-lymphocyte reactivity (From Ref. 2) Miss'~0n Duration Depression (days) Soyus 6, 7, 8 5 Yes Apollo 7-13 6-12 No Skylab It, HI, IV . . . . 28, 59, 84 Yes Apollo-~yuz 9 Yes Salyut 4 , 30, 63 Yes Satyut 6 " 96 No Saly~at6 "140 Yes
Space ShuntS, sT.s-1, 2: 3, 4
2 - 8 -.
Ves (Ref. 3)
,
'
Cultures oflymphocytes, that had been purified from blood samples drawn from crew members before and after flight, were exposed to mitogens. Activation was measured by incorporation of labeled thymidine or uridine into DNA or RNA respectively. A total of 41 astronauts and 12 cosmonaut~were tested. Immunological changes observed in
astronauts Lymphocytes The first report on a reduced efficiency of the immune system after spaceflight was published in 1973 by Soviet investigators 1. The lymphocytes from cosmonauts of the Soyuz 6, 7 and 8 missions showed a depressed reactivity toward T-cell mitogens. Similar effects were later observed on several US and Soviet missions (summarized in Table I and reviewed in Ref. 2). No manned U S space missions took place between the ApolloSoyuz flight in 1975 and the first Space Shuttle flight in 1981. With the beginning of the Shuttle era lymphocyte efficiency began to be regularly tested after each flight. Taylor and Dardano have recently reported the results obtained with lymphocytes of the astronauts of the first four flights 3. The post-flight activation is reduced by between 18 and 6 1 % at optimum mitogen (phytohemagglutinin) concentrations and optimum incubation times. According to the authors the post-flight changes are correlated with the subjectively evaluated increase in the incidence of in-flight stress and not with exposure to hypogravity. In general, recovery of lymphocyte performance to normal pre-flight levels is observed two weeks after landing.
were unchanged after the Skylab missions and after 2, 16, and 18-day Soviet flights, whereas it was significantly higher after the 49-day Salyut-5 flight.
Interferon a-Interferon production has been studied in vitro with lymphocytes taken from cosmonauts before and after space flight 4. Newcastle Disease virus, UV-inactivated was used as the inducer. In two samples the production of interferon was significantly lower after flight, but in the other two it remained unaltered. The induction of interferon production correlated fairly well with the natural killer activity of lymphocytes: The same authors also determined the synthesis of interferon by lymphocytes from noncrew member donors, cultured in space in the presence of four different inducers. In microgravity, production of interferon was almost five times higher than that in the ground controls 4.
Immunoglobulins No significant changes in IgG and I g M levels were found in the Apollo flights and the same is reported for IgG, IgA, IgM, IgD, and IgE after the Skylab missions. Surprisingly, a large increase
of IgA, IgG and IgM serum concentrations was observed after the 49-day Salyut flight 2. This may be related to the secretion of autoantibodies against degradation products produced during the atrophy of skeletal muscles noted in spaceflight. The effect of low gravity on Ig levels was also investigated, by E. W. Voss, during the first Spaeelab mission. Specimens of blood were obtained from four crew members before, during and after flight, and total antibody content as well as specific antibody activities were measured. No significant changes of Ig levels were found s (see discussion below).
High-gravity and low gravity ground simulations It is difficult, at this point, to establish whether the changes observed during spaceflight are due to its gravitational effects or instead to a physiological status of the astronaut which is not related to spaceflight. In 1977, when our proposal to investigate the effect of weightlessness on lymphocyte proliferation on the first Spacelab mission (scheduled at that time for 1979) we began with the study of the behaviour of rat lymphocytes cukured in hypergravity (between 4 and 15 x g). In spite of the scepticism of many colleagues, we were convinced that since gravity had been constant throughout millions of years of biological evolution, altered gravitational conditions would have an important influence on living organisms. The in-vitro transformation of resting into activated lymphocytes by mitogens is not only a good model for testing the efficiency of the immune system but also for the study of cell differentiation. We soon discovered that rat and h u m a n lymphocyte activation was re-
Table II. Protocol of the experiment or, Spacelab
Lysozyme Lysozyme levels were significantly lower than pre-flight in the saliva of cosmonauts after the 49-day Salyut 5 and the 96-day Salyut 6 flights. Slightly higher levels were found in the serum of the Salyut 5 cosmonauts and in two astronauts ofSkylab II. No changes were observed in the serum of the other seven Skylab members.
Complement C3 levels were higher after the Apollo flights, slightly decreased after Skylab II, unchanged after the other Skylab missions, unchanged after a 2-day Soyuz flight, and significantly higher after 16, 18 and 49-day Salyut flights. C4 levels
A synchronous control experiment was run in the ground laboratory at Kennedy Space Center with thd same batch of cells in an identical incubator. The flight samples were handed out to the investigators one hour after landing, after a 10-day mission. Data analysis was performed in Ztirich 5 days after end of the mission.
Immunology 7bday, vol. 6, No. 1, 1985
markably enhanced in cultures exposed to concanavalin A (Con A) and kept at 4 x g (Ref. 6). Conversely, when the cultures were incubated in a rapidly ro~ tating 'Clinostat', activation was depressed by 50% as compared to the 1 x g controls 7. The clinostat is an instrument designed to transform gravity from a vector to a scalar, thus providing simulated but not true weightlessness. Because the launch of Spacelab-1 suffered several delays we could investigate gravitational effects in the centrifuge in more detail. The study was extended to other cell systems like HeLa cells, chicken embryo fibroblasts, sarcoma Galliera cells and Friend leukemia virustransformed cells s. In all instances cell proliferation was enhanced by 20-30 %. However, to our great surprise, glucose consumption in the medium remained the same. The explanation of this apparent contradiction was found by tracking cell movements at high gravity. Using the technique described by Albrecht-Biihler and Lancaster 9 the bottom of the culture flasks were coated with colloidal gold. When the cell moves a clear track is visible in the microscope with dark-field illumination. With HeLa cells we found that cell motility is nil at 10 x g, more energy is therefore available for proliferation s . This finding suggests that the cell is capable of adapting to hypergravity by changing some important functions like motility and division. Hypergravity effects are even much more dramatic when whole blood cultures (diluted 1 : 10 with culture medium) are exposed to Con A at 10 x g. Lymphocyte activation is more than trebled by hypergravity (A. Cogoli and A. Tschopp, unpublished observations). As yet we do not know the reason for this effect in whole blood cultures. It is possible that certain blood components, e.g. erythrocytes or hemin, have a co-mitogenic effect at hypergravity. In fact hemin has been identified as a macrophage-dependent T-cell mitogen 1°. We have used whole blood cultures instead of purified lymphocytes because we will test the efficiency of lymphocytes from crew members in-flight on two Spacelab missions scheduled to fly in 1985 and 1986. The limitations on equipment and crew time make lymphocyte purification in orbit impossible. The results of our ground simulations led us to formulate the hypothesis that microgravity depresses while hypergravity enhances cell proliferation. The effect appears to be more relevant in cells undergoing differentiation than in those undergoing normal division cycles. T h e e x p e r i m e n t on Spacelab-1 We had the opportunity to test our hy-
pothesis under real microgravity conditions during the first Spacelab mission. The main object of the experiment was to establish whether h u m a n lymphocytes in culture are sensitive to microgravity per se, in addition to the effects of stress reported above. The design of the experiment, i.e. the hardware and flight operations, was very simple. Complicated instruments frequently fail irreparably in space, mainly because biological experimentation in orbit is still new so that even unsophisticated experiments which are easily performed in a laboratory on the ground present complex problems when done in a space laboratory. (This will change because ESA and NASA are making great efforts to improve the conditions for biological and biomedical experimentation in space.) Our experiment, described in detail elsewhere i1, consisted of a carry-on incubator (Fig. 1) containing four cell culture chambers and syringes for injection of mitogen, tritiated thymidine and cryopreservative. The incubator operated at a temperature of 37 - 0. I°C, consumed 15 W, and weighed 5.5 kg. It could be connected to the remote acquisition unit
of the spaceship, thus permitting the temperature to be read and checked for proper functioning on the ground. The apparatus and culture chambers were developed and manufactured in our laboratory and had to comply with the severe safety rules of NASA, and with the constraints of weight, volume and power consumption usually encountered in space laboratories. The experiment consisted of exposing lymphocytes in culture to mitogenic concentrations of Con A during spaceflight. Activation was measured by incorporation of tritiated thymidine into DNA. Pre-flight preparations were performed in the NASA Life Sciences facilities in Hangar L at the Kennedy Space Center. The experimental protocol is given in detail in Table II. The flight samples consisted of four cultures sealed in flasks labeled as E, F, G, and H (Fig. 2), A, B, C, and D were the ground control samples. E and A were the unstimulated controls. The experiment has been described and discussed in detail in Ref. 12 but the principal results are given in Fig. 2. The activation of the flight samples was less than
[3H]Thymidine uptake ~0
~5%
a
Glucose consumption E 1 100-
b
,
X ~" 3' X 0O 2-
H-I
600 -
VAH
IAII
0,1 ABCD Ground
EFGH Flight
ABCD Ground
EFGH Flight
Fig. 2. Lymphocyte activation induced by Con A in microgravity. Cultures of human lymphocytes were exposed to mitogenic concentrations of Con A in ground samples B, C, and D and flight samples, F, G and H, respectively. Samples A (ground) and E (flight) were unstimulated controls. (a) Activation measured after 69 h incubation at 37°C as [ 3H].thymidine incorporation into DNA. (b) Glucose remaining in the medium measured with glucose dehydrogenase. The initial concentration of glucose was 1 100 mg 1-1 The standard deviation of triplicate samples is given, except for samples, A, E, F, G, and H in (a), for which it was too low to be shown here. From RO( 12.
Immunology Today, vol. 6, No. 1, 1985
3 % that of the ground controls. However, the cells survived the space flight, since the glucose consumption was only slightly lower in the flown than in the g r o u n d samples (Fig. 2b), and a significant n u m b e r of radiolabeled nuclei were found by autoradiography of the lymphoeytes exposed to C o n A whilst in flight. As discussed above, a decrease of lymphocyte reactivity was predicted by our hypothesis but the extent of the depression was surprising. Although the results are unequivocal, we note that they are from a single experiment and therefore have to be checked on future missions. Moreover, although our observations accord with results obtained from lymphocytes taken from crew m e m b e r s after spaceflight, we cannot extrapolate data from experiments in vitro to changes occurring in vivo. Experiments planned for the D-1 and Spacelab-4 missions in 1985 and 1986 with blood samples drawn pre-, in- and post-flight from crew m e m b e r s should clarify the question of lymphocyte efficiency in space,
Conclusion If we consider what we presently know
about the behaviour of various types of cells at different g-values we can conclude: (a) that most cells investigated are sensitive to gravity; and (b) that the effects seem to be stronger w i t h cells undergoing differentiation - such as lymphocytes which are transformed bY mitogens from a d o r m a n t to an activated state. This also explains the apparent contradiction between our resuk and that of the other immunological experim e n t on SpacelabS: we suggest that gravity effects may become significant only when the i m m u n e system is challenged by an antigen. A n interesting experiment to do in space would be to investigate the antibody response in an animal immunized in-flight. Although the mechanisms involved in gravitational effects on cells are still unknown and a gravity sensor has not been identified we can conclude that, at least in vitro, lymphocytes are sensitiveto gravity.
The work of the authors reported here has been supported by the Swiss National Research Foundation, grants No. 3.034-81 and 3.382-0.82, and by the Board of the Swiss Federal Institutes of Technology.
References 1 Konstantinova, I. V., Antropova, Ye. N,, Legen'kov, V. I. et aL (I973) Space Biol. Aerosp. Med. 7 (6), 48 2 Cogoli,A. (1981) Acta Astronautica 8, 995 3 Taylor, G. R. and Dardano, J. R. (1983) Aviat. SpaceEnviron. Med. (Suppl.) I 54, $55 4 Talas, M., Batkai, L., St6ger, I. et al. (1983) Acta MicrobiologicalAcad. Sci. Hung. 30, 53 5 Voss, Jr., E. W. (1984)Science225, 214 6 Cogoli, A., Vanuchi-Morf, M., B6hringer, H. R. et at. (1979) Life Sci SpaceRes. 17, 219 7 Cogoli,A., Valluchi-Morf, M., Miiller, M. and Briegleb, W. (1980) Aviat. SpaceEnviron. Med. 51, 29 8 Tsehopp, A. and Cogoli, A. (1983) Experientia 39, 1323 9 Albrecht-Buehler, G. and Lancaster, R. M. (1976)J. CellBiol. 71,370 10 Stenzel, K. H., Rubin, A. L. and Novogrodsky, A. (1981)J. Immunol. 127, 2469 II Cogoli,A. and Tschopp, A, (1982)Adv. Biockem. Eng. 22, 1 12 Cogoli, A., Tschopp, A. and Fuehs-Bislin, P. (1984) Science225, 228
Augusto Cogoliand Alexander Tschopp are at the Laboratorium ffir Biochemie, ETH-Zentrum, CH-8092 Ziirich, Switzerland.
Although the immunological changes noted have never had adverse consequences on the health of the astronauts,
they clearly indicate that the efficiency of the immune system is-influenced by spaceflight. Is the cause weightlessness
per se or is it stress? In our continuing investigations we are trying to answer these questions. The advent of the Space Shuttle as an operational vehicle for working in space, the proof that Spacelab is a useful tool for performing scientific experiments in several disciplines and the recent decision to build a permanently manned space station, will require a more broadly based community of scientists and technicians to spend prolonged periods of time (weeks or months) in space. This implies that the criteria for physical certification ofastronauts will be less severe so that physiological changes which have been judged to be minor or not alarming so far may not be perceived as such in the future.
Fig. 1. Incubator with lymphocyte cultures (arrow) installed in rack No. 4 of the Spacelab module during the first Spacelab mission. From left to right astronauts Robert Parker, Byron Lichtenberg, the payload specialist who operated our experiment, Owen Garriott and Ulf Merbold, (Courtesyof NASA.) © 1985, Ehevier Scmnce Publishers B.V., Amsterdam 0167
4919/85/$02.00
Immunology Today, vol. 6, No. 1, 1985
2 Table I. Effect of spaceflight on T-lymphocyte reactivity (From Ref. 2) Miss'~0n Duration Depression (days) Soyus 6, 7, 8 5 Yes Apollo 7-13 6-12 No Skylab It, HI, IV . . . . 28, 59, 84 Yes Apollo-~yuz 9 Yes Salyut 4 , 30, 63 Yes Satyut 6 " 96 No Saly~at6 "140 Yes
Space ShuntS, sT.s-1, 2: 3, 4
2 - 8 -.
Ves (Ref. 3)
,
'
Cultures oflymphocytes, that had been purified from blood samples drawn from crew members before and after flight, were exposed to mitogens. Activation was measured by incorporation of labeled thymidine or uridine into DNA or RNA respectively. A total of 41 astronauts and 12 cosmonaut~were tested. Immunological changes observed in
astronauts Lymphocytes The first report on a reduced efficiency of the immune system after spaceflight was published in 1973 by Soviet investigators 1. The lymphocytes from cosmonauts of the Soyuz 6, 7 and 8 missions showed a depressed reactivity toward T-cell mitogens. Similar effects were later observed on several US and Soviet missions (summarized in Table I and reviewed in Ref. 2). No manned U S space missions took place between the ApolloSoyuz flight in 1975 and the first Space Shuttle flight in 1981. With the beginning of the Shuttle era lymphocyte efficiency began to be regularly tested after each flight. Taylor and Dardano have recently reported the results obtained with lymphocytes of the astronauts of the first four flights 3. The post-flight activation is reduced by between 18 and 6 1 % at optimum mitogen (phytohemagglutinin) concentrations and optimum incubation times. According to the authors the post-flight changes are correlated with the subjectively evaluated increase in the incidence of in-flight stress and not with exposure to hypogravity. In general, recovery of lymphocyte performance to normal pre-flight levels is observed two weeks after landing.
were unchanged after the Skylab missions and after 2, 16, and 18-day Soviet flights, whereas it was significantly higher after the 49-day Salyut-5 flight.
Interferon a-Interferon production has been studied in vitro with lymphocytes taken from cosmonauts before and after space flight 4. Newcastle Disease virus, UV-inactivated was used as the inducer. In two samples the production of interferon was significantly lower after flight, but in the other two it remained unaltered. The induction of interferon production correlated fairly well with the natural killer activity of lymphocytes: The same authors also determined the synthesis of interferon by lymphocytes from noncrew member donors, cultured in space in the presence of four different inducers. In microgravity, production of interferon was almost five times higher than that in the ground controls 4.
Immunoglobulins No significant changes in IgG and I g M levels were found in the Apollo flights and the same is reported for IgG, IgA, IgM, IgD, and IgE after the Skylab missions. Surprisingly, a large increase
of IgA, IgG and IgM serum concentrations was observed after the 49-day Salyut flight 2. This may be related to the secretion of autoantibodies against degradation products produced during the atrophy of skeletal muscles noted in spaceflight. The effect of low gravity on Ig levels was also investigated, by E. W. Voss, during the first Spaeelab mission. Specimens of blood were obtained from four crew members before, during and after flight, and total antibody content as well as specific antibody activities were measured. No significant changes of Ig levels were found s (see discussion below).
High-gravity and low gravity ground simulations It is difficult, at this point, to establish whether the changes observed during spaceflight are due to its gravitational effects or instead to a physiological status of the astronaut which is not related to spaceflight. In 1977, when our proposal to investigate the effect of weightlessness on lymphocyte proliferation on the first Spacelab mission (scheduled at that time for 1979) we began with the study of the behaviour of rat lymphocytes cukured in hypergravity (between 4 and 15 x g). In spite of the scepticism of many colleagues, we were convinced that since gravity had been constant throughout millions of years of biological evolution, altered gravitational conditions would have an important influence on living organisms. The in-vitro transformation of resting into activated lymphocytes by mitogens is not only a good model for testing the efficiency of the immune system but also for the study of cell differentiation. We soon discovered that rat and h u m a n lymphocyte activation was re-
Table II. Protocol of the experiment or, Spacelab
Lysozyme Lysozyme levels were significantly lower than pre-flight in the saliva of cosmonauts after the 49-day Salyut 5 and the 96-day Salyut 6 flights. Slightly higher levels were found in the serum of the Salyut 5 cosmonauts and in two astronauts ofSkylab II. No changes were observed in the serum of the other seven Skylab members.
Complement C3 levels were higher after the Apollo flights, slightly decreased after Skylab II, unchanged after the other Skylab missions, unchanged after a 2-day Soyuz flight, and significantly higher after 16, 18 and 49-day Salyut flights. C4 levels
A synchronous control experiment was run in the ground laboratory at Kennedy Space Center with thd same batch of cells in an identical incubator. The flight samples were handed out to the investigators one hour after landing, after a 10-day mission. Data analysis was performed in Ztirich 5 days after end of the mission.
Immunology 7bday, vol. 6, No. 1, 1985
markably enhanced in cultures exposed to concanavalin A (Con A) and kept at 4 x g (Ref. 6). Conversely, when the cultures were incubated in a rapidly ro~ tating 'Clinostat', activation was depressed by 50% as compared to the 1 x g controls 7. The clinostat is an instrument designed to transform gravity from a vector to a scalar, thus providing simulated but not true weightlessness. Because the launch of Spacelab-1 suffered several delays we could investigate gravitational effects in the centrifuge in more detail. The study was extended to other cell systems like HeLa cells, chicken embryo fibroblasts, sarcoma Galliera cells and Friend leukemia virustransformed cells s. In all instances cell proliferation was enhanced by 20-30 %. However, to our great surprise, glucose consumption in the medium remained the same. The explanation of this apparent contradiction was found by tracking cell movements at high gravity. Using the technique described by Albrecht-Biihler and Lancaster 9 the bottom of the culture flasks were coated with colloidal gold. When the cell moves a clear track is visible in the microscope with dark-field illumination. With HeLa cells we found that cell motility is nil at 10 x g, more energy is therefore available for proliferation s . This finding suggests that the cell is capable of adapting to hypergravity by changing some important functions like motility and division. Hypergravity effects are even much more dramatic when whole blood cultures (diluted 1 : 10 with culture medium) are exposed to Con A at 10 x g. Lymphocyte activation is more than trebled by hypergravity (A. Cogoli and A. Tschopp, unpublished observations). As yet we do not know the reason for this effect in whole blood cultures. It is possible that certain blood components, e.g. erythrocytes or hemin, have a co-mitogenic effect at hypergravity. In fact hemin has been identified as a macrophage-dependent T-cell mitogen 1°. We have used whole blood cultures instead of purified lymphocytes because we will test the efficiency of lymphocytes from crew members in-flight on two Spacelab missions scheduled to fly in 1985 and 1986. The limitations on equipment and crew time make lymphocyte purification in orbit impossible. The results of our ground simulations led us to formulate the hypothesis that microgravity depresses while hypergravity enhances cell proliferation. The effect appears to be more relevant in cells undergoing differentiation than in those undergoing normal division cycles. T h e e x p e r i m e n t on Spacelab-1 We had the opportunity to test our hy-
pothesis under real microgravity conditions during the first Spacelab mission. The main object of the experiment was to establish whether h u m a n lymphocytes in culture are sensitive to microgravity per se, in addition to the effects of stress reported above. The design of the experiment, i.e. the hardware and flight operations, was very simple. Complicated instruments frequently fail irreparably in space, mainly because biological experimentation in orbit is still new so that even unsophisticated experiments which are easily performed in a laboratory on the ground present complex problems when done in a space laboratory. (This will change because ESA and NASA are making great efforts to improve the conditions for biological and biomedical experimentation in space.) Our experiment, described in detail elsewhere i1, consisted of a carry-on incubator (Fig. 1) containing four cell culture chambers and syringes for injection of mitogen, tritiated thymidine and cryopreservative. The incubator operated at a temperature of 37 - 0. I°C, consumed 15 W, and weighed 5.5 kg. It could be connected to the remote acquisition unit
of the spaceship, thus permitting the temperature to be read and checked for proper functioning on the ground. The apparatus and culture chambers were developed and manufactured in our laboratory and had to comply with the severe safety rules of NASA, and with the constraints of weight, volume and power consumption usually encountered in space laboratories. The experiment consisted of exposing lymphocytes in culture to mitogenic concentrations of Con A during spaceflight. Activation was measured by incorporation of tritiated thymidine into DNA. Pre-flight preparations were performed in the NASA Life Sciences facilities in Hangar L at the Kennedy Space Center. The experimental protocol is given in detail in Table II. The flight samples consisted of four cultures sealed in flasks labeled as E, F, G, and H (Fig. 2), A, B, C, and D were the ground control samples. E and A were the unstimulated controls. The experiment has been described and discussed in detail in Ref. 12 but the principal results are given in Fig. 2. The activation of the flight samples was less than
[3H]Thymidine uptake ~0
~5%
a
Glucose consumption E 1 100-
b
,
X ~" 3' X 0O 2-
H-I
600 -
VAH
IAII
0,1 ABCD Ground
EFGH Flight
ABCD Ground
EFGH Flight
Fig. 2. Lymphocyte activation induced by Con A in microgravity. Cultures of human lymphocytes were exposed to mitogenic concentrations of Con A in ground samples B, C, and D and flight samples, F, G and H, respectively. Samples A (ground) and E (flight) were unstimulated controls. (a) Activation measured after 69 h incubation at 37°C as [ 3H].thymidine incorporation into DNA. (b) Glucose remaining in the medium measured with glucose dehydrogenase. The initial concentration of glucose was 1 100 mg 1-1 The standard deviation of triplicate samples is given, except for samples, A, E, F, G, and H in (a), for which it was too low to be shown here. From RO( 12.
Immunology Today, vol. 6, No. 1, 1985
3 % that of the ground controls. However, the cells survived the space flight, since the glucose consumption was only slightly lower in the flown than in the g r o u n d samples (Fig. 2b), and a significant n u m b e r of radiolabeled nuclei were found by autoradiography of the lymphoeytes exposed to C o n A whilst in flight. As discussed above, a decrease of lymphocyte reactivity was predicted by our hypothesis but the extent of the depression was surprising. Although the results are unequivocal, we note that they are from a single experiment and therefore have to be checked on future missions. Moreover, although our observations accord with results obtained from lymphocytes taken from crew m e m b e r s after spaceflight, we cannot extrapolate data from experiments in vitro to changes occurring in vivo. Experiments planned for the D-1 and Spacelab-4 missions in 1985 and 1986 with blood samples drawn pre-, in- and post-flight from crew m e m b e r s should clarify the question of lymphocyte efficiency in space,
Conclusion If we consider what we presently know
about the behaviour of various types of cells at different g-values we can conclude: (a) that most cells investigated are sensitive to gravity; and (b) that the effects seem to be stronger w i t h cells undergoing differentiation - such as lymphocytes which are transformed bY mitogens from a d o r m a n t to an activated state. This also explains the apparent contradiction between our resuk and that of the other immunological experim e n t on SpacelabS: we suggest that gravity effects may become significant only when the i m m u n e system is challenged by an antigen. A n interesting experiment to do in space would be to investigate the antibody response in an animal immunized in-flight. Although the mechanisms involved in gravitational effects on cells are still unknown and a gravity sensor has not been identified we can conclude that, at least in vitro, lymphocytes are sensitiveto gravity.
The work of the authors reported here has been supported by the Swiss National Research Foundation, grants No. 3.034-81 and 3.382-0.82, and by the Board of the Swiss Federal Institutes of Technology.
References 1 Konstantinova, I. V., Antropova, Ye. N,, Legen'kov, V. I. et aL (I973) Space Biol. Aerosp. Med. 7 (6), 48 2 Cogoli,A. (1981) Acta Astronautica 8, 995 3 Taylor, G. R. and Dardano, J. R. (1983) Aviat. SpaceEnviron. Med. (Suppl.) I 54, $55 4 Talas, M., Batkai, L., St6ger, I. et al. (1983) Acta MicrobiologicalAcad. Sci. Hung. 30, 53 5 Voss, Jr., E. W. (1984)Science225, 214 6 Cogoli, A., Vanuchi-Morf, M., B6hringer, H. R. et at. (1979) Life Sci SpaceRes. 17, 219 7 Cogoli,A., Valluchi-Morf, M., Miiller, M. and Briegleb, W. (1980) Aviat. SpaceEnviron. Med. 51, 29 8 Tsehopp, A. and Cogoli, A. (1983) Experientia 39, 1323 9 Albrecht-Buehler, G. and Lancaster, R. M. (1976)J. CellBiol. 71,370 10 Stenzel, K. H., Rubin, A. L. and Novogrodsky, A. (1981)J. Immunol. 127, 2469 II Cogoli,A. and Tschopp, A, (1982)Adv. Biockem. Eng. 22, 1 12 Cogoli, A., Tschopp, A. and Fuehs-Bislin, P. (1984) Science225, 228
Augusto Cogoliand Alexander Tschopp are at the Laboratorium ffir Biochemie, ETH-Zentrum, CH-8092 Ziirich, Switzerland.