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The regulatory effect of histamine on the immune response
CELLULAR
IMMUNOLOGY
The Regulatory
58,366371
(1981)
Effect of Histamine on the Immune Response II. Effect on the in vitro IGG Synthesis’
JACQUES HEBERT,
ROGER BEAUDOIN, MICHELINE AND GA~TAN FRADET
FONTAINE,
Department of Allergy-Immunology, Centre Hospitalier de I’Universitk Lava/, 2705 Boulevard Laurier. Ste-Foy. Quibec GIV 4G2. Canada Received April 21. 1980; accepted June I 9. 1980 Suppressive activity on the proliferative response can be generated by preincubating peripheral blood lymphocytes with Con A or histamine. Histamine-induced suppressive activity is weaker than that of Con A and is possibly not mediated by the same T-cell subpopulations. This study compares both suppressive activity on the in vitro IgG production after PWM stimulation as measured with a modified reverse hemolytic PFC assay. Suppressor cells are added to fresh lymphocytes at either the beginning of the culture with PWM or after they have been cultured for 7 days with PWM. In both cases, PFC are performed on Day 7. In such a system, we can confirm previous reports of decreased IgG synthesis by Con A suppressor cells when they are added at the beginning of the culture. The suppression is then 40 ? 12% as compared to 8 f 9% when suppressor cells are added at the end of the culture. On another hand, histamine suppressor cells lower the IgG production only when added at the end of the culture (43 + 23 vs 3 ? 3%). These results further substantiate the differences between these two modes of suppression, suggesting that different cells could be involved.
INTRODUCTION Abnormalities of immunoregulatory T-cell subpopulations are involved in a growing number of disease states in animals and man (l-3). Their in vitro selective activation by mitogens as Concanavalin A (Con A)’ (4, 5) or histamine (6-10) and their identification by specific cell surface markers (11, 12) have allowed a better definition of these cells and a better understanding of their role. The histamine and Con A-generated suppressor cells (S.C.) can diminish the proliferative response towards mitogens such as phytohemagglutinin (PHA) or Con A (6, 913) and antigens (mixed leukocyte culture, h4LC) (9-13). Both suppressive activities (S.A.) are mediated by T cells with the participation of adherent cells (13). ’ This work was supported by a grant from the Medical Research Council of Canada, MA-6505 * Abbreviations used: Con A, Concanavalin A; SC., suppressorcells; PHA, phytohemagglutinin; MLC, mixed leukocyte culture; S.A., suppressive activity; PWM, pokeweed mitogen; PFC, reverse hemolytic plaque-forming cell; PBL, peripheral blood lymphocytes; FCS, fetal calf serum; SRBC, sheep red blood cell.
366 0008-8749/81/040366-06$02.00/O Copyright 0 1981 by Academic PM. Inc. All right.3 of reproduction in any form reserved.
REGULATION
OF IgG SYNTHESIS
BY HISTAMINE
367
The histamine-induced S.A. is less prominent than that induced by Con A but it is not clear yet whether or not both types of suppressor cells are identical. Regulatory T cells also control immunoglobulin synthesis (4, 5). So, Con Ainduced S.C. do suppress the in vitro synthesis of IgG stimulated by pokeweed mitogen (PWM) when they are added early in the culture (5). The present study aims to measure the effects of histamine-induced S.A. on in vitro IgG synthesis, as measured by a modified reverse hemolytic plaque (PFC) assay (14), and to compare it to the already described Con A-induced S.A. MATERIALS
AND METHODS
Subjects. Blood from nonatopic normal volunteers (20-40 years of age) was used throughout this study. PuriJcation of lymphocytes. Peripheral blood lymphocytes (PBL) were obtained following centrifugation of heparinized (10 U/ml) fresh blood from healthy donors over a gradient of density (Ficoll-Hypaque) (9). PBL were washed three times in Hanks’ balanced salt solution (Gibco) and counted. Viability was checked using the trypan blue dye exclusion test and always exceeded 98%. Culture conditions. PBL were adjusted to a concentration of l-2 X 106/ml in culture medium (RPM1 1640, Gibco) supplemented with 10% fetal calf serum (FCS, Flow Labs.), 1% L-glutamine (Gibco) and antibiotics: 100 U/ml penicillin, 100 pug/ml streptomycin, and 100 pg/ml gentamycin. PBL were then stimulated with PWM (Gibco, 10 pi/ml) and incubated for 7 days at 37°C in a humidified atmosphere of 95% 02-5% COZ (6, 9). At the end of the culture period, cells were washed and counted and the concentration adjusted to 1 X lo6 viable cells/ml for the PFC assay. Reverse hemolytic plaque assay. A modified reverse hemolytic plaque assay was used to measure the synthesis of IgG (14). Briefly, sheep red blood cells (SRBC) were coated with a purified anti-Fab using chromium chloride. Coupled-SRBC (30 ~1) were then mixed with 50 ~1 of cultured lymphocytes appropriately diluted, 50 ~1 of the developing anti-IgG antiserum at optimal dilution (1: 120) and 50 ~1 of SRBC-adsorbed guinea pig complement (Cedarlane) diluted 1:2 with cold saline. This mixture was then pipetted between two microscope slides held in position by double coated tape (No. 410, 3M Company) placed at both ends and in the middle of the slides (15). The thickness of the tape leaves two microchambers where the cells could extend by capillarity and form a monolayer. The slides were then sealed by slightly dipping the sides into a melted mixture of paraffin:petroleum jelly ( 1:1). After 2 hr of incubation at 37°C PFC were counted under low magnification. The presence of a lymphoid cell in the center of the hemolytic plaque was checked microscopically. Results are expressed as number of PFC per lo6 viable lymphocytes. Generation of suppressor cells. PBL were incubated at 37°C in a humidified atmosphere of 95% O,-5% CO, with either 10e3M histamine (Fisher) for 3% hr or lOkg/ml of Con A for 48 hr. At the end of the incubation the cells were washed and irradiated (3000 rad) (6, 9). Effects of XC. on ZgG synthesis. Increasing numbers of suppressor cells were
368
HfiBERT ET AL.
added to a constant number of PBL (1 X lo6 cells) in order to have the following ratios suppressor/target cells: 0.125/l to 8/l. The suppressor cells were added to allogeneic PBL on the same day as PWM (Day 0) or to the PWM-stimulated PBL after 7 days of culture (Day 7). After the completion of the culture, the cells are washed before the PFC response is determined. RESULTS Synthesis of IgG in Presence of Histamine-Induced Suppressor Cells PBL, upon in vitro PWM stimulation, synthesize immunoglobulins (5, 14, 16, 17). Addition of allogeneic histamine-induced suppressor cells at the end of the culture, on Day 7, caused a significant suppression of the IgG response (Fig. 1), optimally at ratios ranging from 0.5/l to 2/l. On another hand, addition of S.C. at the beginning of the culture does not suppress the synthesis of IgG (Fig. 2), at all the cell ratios used (S.C./responding cells: 0.125/l to 8/l). Comparable results are obtained with autologous S.C. (data not shown). Synthesis of IgG in Presence of Con A-Induced Suppressor Cells Con A-induced S.C. do suppress well IgG synthesis (40 f 12%) when added at the beginning of the culture (at optimal ratio I/ 1) (Fig. 3) and not when added at the end of the culture (8 k 9%). Those findings confirm most of the previous studies (5) and are in opposition to the findings with histamine-induced S.A. (Fig. 3).
32
supp.(xtS.D.)
P
328 N.S.
2SsS
2 43?23
SO.25
0
CELLS PREINCUBATED
WITH MEDIUM
m
CELLS PREINCUBATED
WITHHISTAMINE
1 34220
0.5 23221
~325 10213
<0.0025
401
NS.
RATIO
S.C./RESP.
FIG. 1. Suppression of the number of IgG-PFC in the presence of cells preincubated with or without histamine. S.C. are added on Day 7, immediately before the PFC assay. Different ratios of suppressor cells/responding (IgG-secreting) cells are compared. Mean f sd of 16 experiments.
REGULATION
OF IgG SYNTHESIS
369
BY HISTAMINE
32
28
ISUPP’S.D.13’3 P
NS
0
CELLS PREINCUBATED
WITH MEDIUM
m
CELLS PREINCUBATED
WITH HISTAMINE
3t4
5ta
2+5
Ns
NS
Ns
I0 I.5 1+4
RATIOSC
/RESP
NS
FIG. 2. Suppression of the number of IgG-PFC in the presence of cells preincubated with or without histamine. S.C. are added to responding cells in different ratios on Day 0 along with PWM. Mean f sd of 10 experiments.
DISCUSSION A number of differences have already been stressed between histamine and Con A-induced S.C. Both suppress the proliferative response to antigen (MLC) and mitogen (PHA and Con A) but the S.A. induced by Con A is more prominent (6, 9, 13). A possible explanation for this observation could be that suppressor cells have fewer H-2 receptors than Con A receptors or that the affinity of these H-2 receptors for histamine is lower. The possibility of two separate suppressor cell populations having receptors for either Con A or histamine cannot be dismissed. 0
CELLS PREINCUBATEO WITH CONA
m
CELLS PREINCUEATED WITH HISTAMINE
FIG. 3. Comparison between the percentage of suppression observed with Con A-activated histamine-activated cells as seen on Day 0 or 7.
cells and
370
HEBERT ET AL.
The present study also suggests a functional difference between these two types of suppression. Indeed the kinetics and mechanisms of suppression of the PWM-induced PFC response of human PBL by Con A-activated S.C. have been investigated (5). The Con A-activated suppressor cells must be present early in the process of activation of human PBL in order to suppress effectively. Our work confirms the previous studies: a significant suppression of IgG response is seen when the suppressor cells are added on the same day as PWM (40 -t 12%) and no suppression is seen when added at the end of the culture (8 _+ 9%). The same observation has been made in the murine system: Con A-activated suppressor cells must be present early in the antigenic specific activation of spleen cells toward anti-SRBC PFC formation (18, 19). However, the effects of Con A suppressor cells were not manifest until late in the culture ( 18, 20) probably due to the action of suppressor cells on rapidly dividing B cells or B-cell precursors and probably not on helper T cells ( 18, 21). The histamine-induced S.C. do not suppress the IgG synthesis when added on the same day as PWM. A significant suppression (43 f 23%, P ~0.0025) is seen, however, when S.C. are added on Day 7, after the culture is completed. This suppression is optimal at ratios S.C./responding cells ranging from 0.5/l to 2/l. The S.A. decreasesas the number of S.C. increases over a ratio of 2/ 1. The reasons for this decrease are unclear: “crowding” effect that inhibits the action of S.C., addition of helper cells along with S.C. that begin to show their effect as the suppression tends to plateau (22). These hypotheses are currently under study. These observations suggest that the histamine-induced suppressor cells do not act by blocking the proliferation of B cells or B-cell precursors as opposed to the Con A-generated suppressor cells. They could act by inhibiting the synthesis or release of IgG by mature B cells. It could be interesting to postulate that this mode of immunoregulation is involved in the control of IgE synthesis as well. Indeed, a defect of histamine-induced S.A. is reported in atopy (8, 10,23). The refractoriness to in vitro induction may then reflect an already on going in vivo activation or modulation of these S.C. Furthermore, antigen-specific S.C. generated in the process of immunotherapy carry a receptor for histamine (24). REFERENCES 1. Waldmann, T. A., Ann. Int. Med. 88, 226, 1978. 2. Gershon, R. K., Transplant. Rev. 26, 170, 1975. 3. Waldmann, T. A., Broder, S., and Krakauer, R., In “Suppressor Cells in Immunity (International Symposium)” (S. K. Singhal and IV. R. St. C. Sinclair, Eds.), pp. 182-187,Universityof Western Ontario, London, Canada, 1975. 4. Shou, L., Schwartz, S. A., and Good, R. A., J. Exp. Med. 113, 1100, 1976. 5. Haynes, B. F., and Fauci, A. S., J. Immunol. 118, 2281, 1977. 6. Hebert, J., Beaudoin, R., and Aubin, M., Union Med. Canad. 107, 371, 1978. 7. Wang, S. R., and Zweiman, B., Cell. Immunol. 36, 28, 1978. 8. Martinez, J. D., Santos, J., Stechschulte, D. J., and Abdou, N. I., J. Allergy Cfin. Immunol. 64, 485, 1979. 9. Hebert, J., Beaudoin, R., Aubin, M., and Fontaine, M., Cell. Immunol. 54, 49, 1980. 10. Rocklin, R. E., and Haberek-Davidson, A., “Abstract 113, Meeting of American Academy of Allergy, Atlanta, 1980.” 11. Moretta, L., Webb, S. R., Grossi, C. E., Lydyard, P. M., and Cooper, M. D., J. Exp. Med. 146, 484. 1977.
REGULATION 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.
OF IgG SYNTHESIS
BY HISTAMINE
371
Gupta, S., Clin. Bull. 3, 100, 1978. Hebert, J., Beaudoin, R., and Aubin, M., C/in. Res. 26, 857A, 1978. Beaudoin, R., Valet, J. P., and Hebert, J., J. Immunol. Methods, 14, 35, 91, 1980. Cunningham, A. J., and Szenberg, A., Immunology 14, 599, 1968. Waldmann, T. A., Broder, S., Blaese, R. M., Durm, M., Blackman, M., and Strober, W., Lancet 2, 609, 1974. Abdou, N. I., Sagawa, A., Pascual, E., Hebert, J., and Sadegher, S., Clin. Immunol. Immunopathol. 6, 192, 1976. Haynes, B. F., and Fauci, A. S., J. Immunol. 121, 559, 1978. Haynes, B. F., and Fauci, A. S., Cell. Immunol. 44, 157, 1979. Haynes, B. F., and Fauci, A. S., Cell. Immunol. 44, 169, 1979. Touraine, J. L., Hadden, J. W., and Good, R. A., Proc. Nat. Acad. Sci. USA 74, 3414, 1977. Sakane, T., and Green, I., J. Immunol. 119, 1169, 1977. Htbert, J., Fontaine, M., Beaudoin, R., and Cloutier, R., Union Med. Canad., 23, in press. Rocklin, R. E., Greineder, D. K., and Sheffer, A. L., Clin. Res. 27, 474A, 1979.
IMMUNOLOGY
The Regulatory
58,366371
(1981)
Effect of Histamine on the Immune Response II. Effect on the in vitro IGG Synthesis’
JACQUES HEBERT,
ROGER BEAUDOIN, MICHELINE AND GA~TAN FRADET
FONTAINE,
Department of Allergy-Immunology, Centre Hospitalier de I’Universitk Lava/, 2705 Boulevard Laurier. Ste-Foy. Quibec GIV 4G2. Canada Received April 21. 1980; accepted June I 9. 1980 Suppressive activity on the proliferative response can be generated by preincubating peripheral blood lymphocytes with Con A or histamine. Histamine-induced suppressive activity is weaker than that of Con A and is possibly not mediated by the same T-cell subpopulations. This study compares both suppressive activity on the in vitro IgG production after PWM stimulation as measured with a modified reverse hemolytic PFC assay. Suppressor cells are added to fresh lymphocytes at either the beginning of the culture with PWM or after they have been cultured for 7 days with PWM. In both cases, PFC are performed on Day 7. In such a system, we can confirm previous reports of decreased IgG synthesis by Con A suppressor cells when they are added at the beginning of the culture. The suppression is then 40 ? 12% as compared to 8 f 9% when suppressor cells are added at the end of the culture. On another hand, histamine suppressor cells lower the IgG production only when added at the end of the culture (43 + 23 vs 3 ? 3%). These results further substantiate the differences between these two modes of suppression, suggesting that different cells could be involved.
INTRODUCTION Abnormalities of immunoregulatory T-cell subpopulations are involved in a growing number of disease states in animals and man (l-3). Their in vitro selective activation by mitogens as Concanavalin A (Con A)’ (4, 5) or histamine (6-10) and their identification by specific cell surface markers (11, 12) have allowed a better definition of these cells and a better understanding of their role. The histamine and Con A-generated suppressor cells (S.C.) can diminish the proliferative response towards mitogens such as phytohemagglutinin (PHA) or Con A (6, 913) and antigens (mixed leukocyte culture, h4LC) (9-13). Both suppressive activities (S.A.) are mediated by T cells with the participation of adherent cells (13). ’ This work was supported by a grant from the Medical Research Council of Canada, MA-6505 * Abbreviations used: Con A, Concanavalin A; SC., suppressorcells; PHA, phytohemagglutinin; MLC, mixed leukocyte culture; S.A., suppressive activity; PWM, pokeweed mitogen; PFC, reverse hemolytic plaque-forming cell; PBL, peripheral blood lymphocytes; FCS, fetal calf serum; SRBC, sheep red blood cell.
366 0008-8749/81/040366-06$02.00/O Copyright 0 1981 by Academic PM. Inc. All right.3 of reproduction in any form reserved.
REGULATION
OF IgG SYNTHESIS
BY HISTAMINE
367
The histamine-induced S.A. is less prominent than that induced by Con A but it is not clear yet whether or not both types of suppressor cells are identical. Regulatory T cells also control immunoglobulin synthesis (4, 5). So, Con Ainduced S.C. do suppress the in vitro synthesis of IgG stimulated by pokeweed mitogen (PWM) when they are added early in the culture (5). The present study aims to measure the effects of histamine-induced S.A. on in vitro IgG synthesis, as measured by a modified reverse hemolytic plaque (PFC) assay (14), and to compare it to the already described Con A-induced S.A. MATERIALS
AND METHODS
Subjects. Blood from nonatopic normal volunteers (20-40 years of age) was used throughout this study. PuriJcation of lymphocytes. Peripheral blood lymphocytes (PBL) were obtained following centrifugation of heparinized (10 U/ml) fresh blood from healthy donors over a gradient of density (Ficoll-Hypaque) (9). PBL were washed three times in Hanks’ balanced salt solution (Gibco) and counted. Viability was checked using the trypan blue dye exclusion test and always exceeded 98%. Culture conditions. PBL were adjusted to a concentration of l-2 X 106/ml in culture medium (RPM1 1640, Gibco) supplemented with 10% fetal calf serum (FCS, Flow Labs.), 1% L-glutamine (Gibco) and antibiotics: 100 U/ml penicillin, 100 pug/ml streptomycin, and 100 pg/ml gentamycin. PBL were then stimulated with PWM (Gibco, 10 pi/ml) and incubated for 7 days at 37°C in a humidified atmosphere of 95% 02-5% COZ (6, 9). At the end of the culture period, cells were washed and counted and the concentration adjusted to 1 X lo6 viable cells/ml for the PFC assay. Reverse hemolytic plaque assay. A modified reverse hemolytic plaque assay was used to measure the synthesis of IgG (14). Briefly, sheep red blood cells (SRBC) were coated with a purified anti-Fab using chromium chloride. Coupled-SRBC (30 ~1) were then mixed with 50 ~1 of cultured lymphocytes appropriately diluted, 50 ~1 of the developing anti-IgG antiserum at optimal dilution (1: 120) and 50 ~1 of SRBC-adsorbed guinea pig complement (Cedarlane) diluted 1:2 with cold saline. This mixture was then pipetted between two microscope slides held in position by double coated tape (No. 410, 3M Company) placed at both ends and in the middle of the slides (15). The thickness of the tape leaves two microchambers where the cells could extend by capillarity and form a monolayer. The slides were then sealed by slightly dipping the sides into a melted mixture of paraffin:petroleum jelly ( 1:1). After 2 hr of incubation at 37°C PFC were counted under low magnification. The presence of a lymphoid cell in the center of the hemolytic plaque was checked microscopically. Results are expressed as number of PFC per lo6 viable lymphocytes. Generation of suppressor cells. PBL were incubated at 37°C in a humidified atmosphere of 95% O,-5% CO, with either 10e3M histamine (Fisher) for 3% hr or lOkg/ml of Con A for 48 hr. At the end of the incubation the cells were washed and irradiated (3000 rad) (6, 9). Effects of XC. on ZgG synthesis. Increasing numbers of suppressor cells were
368
HfiBERT ET AL.
added to a constant number of PBL (1 X lo6 cells) in order to have the following ratios suppressor/target cells: 0.125/l to 8/l. The suppressor cells were added to allogeneic PBL on the same day as PWM (Day 0) or to the PWM-stimulated PBL after 7 days of culture (Day 7). After the completion of the culture, the cells are washed before the PFC response is determined. RESULTS Synthesis of IgG in Presence of Histamine-Induced Suppressor Cells PBL, upon in vitro PWM stimulation, synthesize immunoglobulins (5, 14, 16, 17). Addition of allogeneic histamine-induced suppressor cells at the end of the culture, on Day 7, caused a significant suppression of the IgG response (Fig. 1), optimally at ratios ranging from 0.5/l to 2/l. On another hand, addition of S.C. at the beginning of the culture does not suppress the synthesis of IgG (Fig. 2), at all the cell ratios used (S.C./responding cells: 0.125/l to 8/l). Comparable results are obtained with autologous S.C. (data not shown). Synthesis of IgG in Presence of Con A-Induced Suppressor Cells Con A-induced S.C. do suppress well IgG synthesis (40 f 12%) when added at the beginning of the culture (at optimal ratio I/ 1) (Fig. 3) and not when added at the end of the culture (8 k 9%). Those findings confirm most of the previous studies (5) and are in opposition to the findings with histamine-induced S.A. (Fig. 3).
32
supp.(xtS.D.)
P
328 N.S.
2SsS
2 43?23
SO.25
0
CELLS PREINCUBATED
WITH MEDIUM
m
CELLS PREINCUBATED
WITHHISTAMINE
1 34220
0.5 23221
~325 10213
<0.0025
401
NS.
RATIO
S.C./RESP.
FIG. 1. Suppression of the number of IgG-PFC in the presence of cells preincubated with or without histamine. S.C. are added on Day 7, immediately before the PFC assay. Different ratios of suppressor cells/responding (IgG-secreting) cells are compared. Mean f sd of 16 experiments.
REGULATION
OF IgG SYNTHESIS
369
BY HISTAMINE
32
28
ISUPP’S.D.13’3 P
NS
0
CELLS PREINCUBATED
WITH MEDIUM
m
CELLS PREINCUBATED
WITH HISTAMINE
3t4
5ta
2+5
Ns
NS
Ns
I0 I.5 1+4
RATIOSC
/RESP
NS
FIG. 2. Suppression of the number of IgG-PFC in the presence of cells preincubated with or without histamine. S.C. are added to responding cells in different ratios on Day 0 along with PWM. Mean f sd of 10 experiments.
DISCUSSION A number of differences have already been stressed between histamine and Con A-induced S.C. Both suppress the proliferative response to antigen (MLC) and mitogen (PHA and Con A) but the S.A. induced by Con A is more prominent (6, 9, 13). A possible explanation for this observation could be that suppressor cells have fewer H-2 receptors than Con A receptors or that the affinity of these H-2 receptors for histamine is lower. The possibility of two separate suppressor cell populations having receptors for either Con A or histamine cannot be dismissed. 0
CELLS PREINCUBATEO WITH CONA
m
CELLS PREINCUEATED WITH HISTAMINE
FIG. 3. Comparison between the percentage of suppression observed with Con A-activated histamine-activated cells as seen on Day 0 or 7.
cells and
370
HEBERT ET AL.
The present study also suggests a functional difference between these two types of suppression. Indeed the kinetics and mechanisms of suppression of the PWM-induced PFC response of human PBL by Con A-activated S.C. have been investigated (5). The Con A-activated suppressor cells must be present early in the process of activation of human PBL in order to suppress effectively. Our work confirms the previous studies: a significant suppression of IgG response is seen when the suppressor cells are added on the same day as PWM (40 -t 12%) and no suppression is seen when added at the end of the culture (8 _+ 9%). The same observation has been made in the murine system: Con A-activated suppressor cells must be present early in the antigenic specific activation of spleen cells toward anti-SRBC PFC formation (18, 19). However, the effects of Con A suppressor cells were not manifest until late in the culture ( 18, 20) probably due to the action of suppressor cells on rapidly dividing B cells or B-cell precursors and probably not on helper T cells ( 18, 21). The histamine-induced S.C. do not suppress the IgG synthesis when added on the same day as PWM. A significant suppression (43 f 23%, P ~0.0025) is seen, however, when S.C. are added on Day 7, after the culture is completed. This suppression is optimal at ratios S.C./responding cells ranging from 0.5/l to 2/l. The S.A. decreasesas the number of S.C. increases over a ratio of 2/ 1. The reasons for this decrease are unclear: “crowding” effect that inhibits the action of S.C., addition of helper cells along with S.C. that begin to show their effect as the suppression tends to plateau (22). These hypotheses are currently under study. These observations suggest that the histamine-induced suppressor cells do not act by blocking the proliferation of B cells or B-cell precursors as opposed to the Con A-generated suppressor cells. They could act by inhibiting the synthesis or release of IgG by mature B cells. It could be interesting to postulate that this mode of immunoregulation is involved in the control of IgE synthesis as well. Indeed, a defect of histamine-induced S.A. is reported in atopy (8, 10,23). The refractoriness to in vitro induction may then reflect an already on going in vivo activation or modulation of these S.C. Furthermore, antigen-specific S.C. generated in the process of immunotherapy carry a receptor for histamine (24). REFERENCES 1. Waldmann, T. A., Ann. Int. Med. 88, 226, 1978. 2. Gershon, R. K., Transplant. Rev. 26, 170, 1975. 3. Waldmann, T. A., Broder, S., and Krakauer, R., In “Suppressor Cells in Immunity (International Symposium)” (S. K. Singhal and IV. R. St. C. Sinclair, Eds.), pp. 182-187,Universityof Western Ontario, London, Canada, 1975. 4. Shou, L., Schwartz, S. A., and Good, R. A., J. Exp. Med. 113, 1100, 1976. 5. Haynes, B. F., and Fauci, A. S., J. Immunol. 118, 2281, 1977. 6. Hebert, J., Beaudoin, R., and Aubin, M., Union Med. Canad. 107, 371, 1978. 7. Wang, S. R., and Zweiman, B., Cell. Immunol. 36, 28, 1978. 8. Martinez, J. D., Santos, J., Stechschulte, D. J., and Abdou, N. I., J. Allergy Cfin. Immunol. 64, 485, 1979. 9. Hebert, J., Beaudoin, R., Aubin, M., and Fontaine, M., Cell. Immunol. 54, 49, 1980. 10. Rocklin, R. E., and Haberek-Davidson, A., “Abstract 113, Meeting of American Academy of Allergy, Atlanta, 1980.” 11. Moretta, L., Webb, S. R., Grossi, C. E., Lydyard, P. M., and Cooper, M. D., J. Exp. Med. 146, 484. 1977.
REGULATION 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.
OF IgG SYNTHESIS
BY HISTAMINE
371
Gupta, S., Clin. Bull. 3, 100, 1978. Hebert, J., Beaudoin, R., and Aubin, M., C/in. Res. 26, 857A, 1978. Beaudoin, R., Valet, J. P., and Hebert, J., J. Immunol. Methods, 14, 35, 91, 1980. Cunningham, A. J., and Szenberg, A., Immunology 14, 599, 1968. Waldmann, T. A., Broder, S., Blaese, R. M., Durm, M., Blackman, M., and Strober, W., Lancet 2, 609, 1974. Abdou, N. I., Sagawa, A., Pascual, E., Hebert, J., and Sadegher, S., Clin. Immunol. Immunopathol. 6, 192, 1976. Haynes, B. F., and Fauci, A. S., J. Immunol. 121, 559, 1978. Haynes, B. F., and Fauci, A. S., Cell. Immunol. 44, 157, 1979. Haynes, B. F., and Fauci, A. S., Cell. Immunol. 44, 169, 1979. Touraine, J. L., Hadden, J. W., and Good, R. A., Proc. Nat. Acad. Sci. USA 74, 3414, 1977. Sakane, T., and Green, I., J. Immunol. 119, 1169, 1977. Htbert, J., Fontaine, M., Beaudoin, R., and Cloutier, R., Union Med. Canad., 23, in press. Rocklin, R. E., Greineder, D. K., and Sheffer, A. L., Clin. Res. 27, 474A, 1979.