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Humoral and cell-mediated immune responses in chickens with infectious bursal disease
Veterinary Microbiology, 7 (1982) 383--387 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
383
Short Communication H U M O R A L AND C E L L - M E D I A T E D IMMUNE RESPONSES IN CHICKENS WITH INFECTIOUS BURSAL DISEASE
B. PANIGRAHY', L.K. MISRA2 and L.G. ADAMS 3 Departments of'Veterinary Microbiology, and 2Veterinary Pathology, College of Veterinary Medicine, Texas A & M University, College Station, TX 77843 (U.S.A.) 3Texas Agricultural Experiment Station, College Station, TX 77843 (U.S.A.)
(Accepted 15 April 1982)
ABSTRACT
Panigrahy, B., Misra, L.K. and Adams, L.G., 1982. Humoral and cell-mediated immune responses in chickens with infectious bursal disease. Vet. MicrobioL, 7: 383--387. Primary and secondary immune responses to Newcastle disease virus (NDV) was evaluated in chickens infected with infectious bursal disease virus (IBDV) at one and 28 days of age. The geometric mean primary hemagglutination-inhibition antibody titers (GMT) of chickens infected with IBDV at one day of age was significantly lower (P < 0.01) than those infected at 28 days of age. Infection with IBDV had no influence on secondary immune response to NDV. The effect of IBDV infection at one day of age on the cell-mediated immunity of chickens was evaluated by skin allograft acceptance or survival time. There was no significant difference between the percentage of grafts accepted in IBDV infected and noninfeeted control chickens. However, the mean graft survival time in the IBDV infected chickens was significantly longer (P ~< 0.05) than those in the control group. This suggested a suppression of cell-mediated immunity due to IBDV infection.
INTRODUCTION I n f e c t i o u s bursal disease (IBD) is a n a t u r a l l y o c c u r r i n g , virus-induced imm u n e d e f i c i e n c y o f c h i c k e n s c h a r a c t e r i z e d b y necrosis a n d d e p l e t i o n o f l y m p h o i d e l e m e n t s o f the b u r s a o f Fabricius. T h e b u r s a seeds B cell (bursad e p e n d e n t l y m p h o c y t e ) clones t o peripheral l y m p h o i d tissues d u r i n g emb r y o n a t i o n a n d t h e first f e w d a y s o f life. I n f e c t i o n o f chicks w i t h t h e inf e c t i o u s bursal disease virus ( I B D V ) at this t i m e has been s h o w n t o suppress h u m o r a l i m m u n e responses t o various antigens (Cho, 1 9 7 0 ; Allan et al., 1 9 7 2 ; F a r a g h e r et al., 1 9 7 2 , 1 9 7 4 ; H u d s o n et al., 1 9 7 5 ; W y e t h , 1 9 7 5 ; I v a n y i and Morris, 1 9 7 6 ; G i a m b r o n e et al., 1 9 7 6 , 1 9 7 7 a , b). O n t h e o t h e r h a n d , in i m m u n o l o g i c a l l y m a t u r e c h i c k e n s , i.e., at 28 d a y s o f age, I B D m a y p r o d u c e o n l y a partial o r n o i m m u n e suppression. I n a d d i t i o n t o l y m p h o i d d e g e n e r a t i o n o f t h e bursa, I B D V causes m o d e r a t e
0378-1135/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company
384 to severe lymphoid necrosis of the thymus and the spleen (Helmboldt and Garner, 1964; Cheville, 1967). The T cells (thymus-dependent lymphocytes) play a direct role in cell-mediated immunity. It can be postulated that the IBDV infection would interfere with immune reactions dependent on both the bursa and the thymus. The purpose of this study was to evaluate: (a) the effect of IBDV infection at one and 28 days of age on primary and secondary humoral immune response to Newcastle disease virus (NDV); and (b) cell-mediated immune response by skin aUograft survival in chickens infected at one day of age. MATERIALS AND METHODS
Stock IBDV. Bursal tissue from chickens naturally infected with IBDV was passaged once in 4-week-old susceptible chickens. The spleens were collected four days after infection. A 10% (w/v) spleen suspension in Hanks' balanced salt solution was prepared and assayed in 10-day-old specific pathogen free (SPAFAS Inc., Norwich, CT 06360} chicken embryos by the choriollantoic membrane route of inoculation. The titer of IBDV was 103.4 ELDs0/ml of the suspension. Chickens. One-day-old male White Leghorn chicks, free of demonstrable maternal antibody to IBDV by the agar gel precipitin test, were obtained from a commercial hatchery. These are non-inbred chicks from an incross line developed from mating of four inbred populations. Humoral immunity. Day-old chicks were distributed into three groups of 15 chicks each. Group 1 chicks served as noninfected controls. Chicks in groups 2 and 3 were infected with IBDV, respectively, at one and 28 days of age. Each chick was infected by conjunctival (one drop in each eye) and oral (0.2 ml) inoculation of the infectious spleen suspension. At 32 days of age, chickens in each group were immunized with NDV (B1 strain; titer, 104.2 TCIDs0/0.1 ml) by the conjunctival (one drop in each eye) route. Individual blood sera were collected 14 days following immunization and, at this time, each chick was reimmunized with NDV as before. Seven day s after the second immunization, individual blood serum samples were collected. The primary and secondary hemagglutination-inhibition (HI) antibody titers were measured by microtiter method. Statistical analysis of geometric mean HI antibody titers (GMT) was done by analysis of variance and Duncan's multiple-range test. Cell-mediated immunity. Day-old chicks were randomly distributed into t w o groups. One group of 50 chicks served as noninfected controls. Another group of 55 chicks was infected with IBDV at one day of age as previously described. At 5 days of age the chicks in each group received skin allografts. The donors and recipients were selected at random. Skin grafting was done
385 according to the techniques of Billingham and Medawar (1951) as modified by Gleason and Fanguy (1964). Grafts were examined for rejection or acceptance twice weekly for 10 weeks. Feather growth over the transplanted skin through the 10-week observation period was regarded as acceptance of the graft. On the other hand, formation of a scab followed by sloughing of skin was considered as the end point of graft rejection. Statistical analysis of skin graft survival was done by the Chi-Square method and the Student's t-test. RESULTS AND DISCUSSION
Humoral immunity. The primary GMT for NDV (Table I) in the noninfected control chickens and those infected with IBDV at one and 28 days of age, respectively, was 36.44, 10.08, and 20.74. Chickens infected at one day of age had significantly less (P < 0.01) GMT than the controls and those infected at 28 days of age. There was no significant difference in GMT in the latter two groups. Seeding of B cell clones to the peripheral lymphoid tissues occurs during e m b r y o n a t i o n and the first days of life (Cooper et al., 1969; Ivanyi, 1973, 1975). Therefore, it m a y be assumed that IBDV infection in ovo or on the day of hatching would result in suppression of humoral immune response. However, at 28 days of age, the chickens is immunologically mature, and infection with IBDV at this age would cause only a transient immunosuppression. The results of the present study and those of others (Faragher et al., 1972; Allan et al., 1972; Giambrone et al., 1976, 1977a) concur with these assumptions. The secondary GMT to NDV in control chickens and those infected with IBDV at one and 28 days of age, respectively, were 48.50, 38.50, and 36.15. These values were n o t significantly different. Although IBDV infection at one day of age caused a suppression of primary immune response to NDV, there was no suppression of the secondary immune response. Therefore, immune suppression because of IBDV infection as early as one day of age is n o t an irreversible process. TABLE I G e o m e t r i c m e a n primary and s e c o n d a r y h e m a g g l u t i n a t i o n - i n h i b i t i o n a n t i b o d y titers (GMT) to N e w c a s t l e disease virus in c h i c k e n s infected w i t h infectious bursal disease virus ( I B D V ) at one and 28 d a y s o f age Treatment
groups
N o n i n f e c t e d control I B D V i n f e c t i o n at one day o f age I B D V i n f e c t i o n at 28 d a y s of age
No. of chickens Primary GMT
S e c o n d a r y GMT
15
3 6 . 4 4 a*
48.50 a
15
10.08 b
38.50 a
15
20.74 a
36.15 a
*Values in each c o l u m n d e n o t e d b y different letters are significantly different at P ~<0.01 level.
386
Cell-mediated immunity. Results on the prolongation of skin graft survival in infected and noninfected chickens are presented in Table II. Twenty-eight of 55 (51%) of the infected and 19 of 50 (38%) of the noninfected birds accepted skin allografts. All chickens that accepted grafts had normal feather development. Although the percentage of chickens accepting the grafts was higher in the infected than in the noninfected group, the difference was n o t statistically significant. However, the mean graft survival time in the IBDVinfected group was significantly (P ~< 0.05) longer (48.07 days) than in the noninfected group (36.26 days). Prolonged skin graft survival in chickens infected at one day of age may be attributed to a suppression of cell-mediated immunity. TABLEII Prolongation of skin allograft survival in chickens infected with infectious bursal disease virus (IBDV) Treatment groups
No. of chickens grafted
No. of chickens accepting grafts
Percent graft acceptance
Mean graft survival time (days)
Noninfected control IBDV infection at one day of age
50
19
38 a*
36.26 a
55
28
51 a
48.07 b
*Values in each column denoted by different letters are significantly different at P ~< 0.05 level.
In conclusion, chickens infected with IBDV at one day of age had significantly lower (P ~< 0.01) antibody titers to NDV than the chickens infected at 28 days of age. However, the immunosuppressive effect of IBDV on the secondary immune response was n o t observed. Prolonged skin graft survival in chickens infected at one day of age suggested suppression of cell-mediated immunity.
REFERENCES Allan, W.H., Faragher, J.T. and Cullen, G.A., 1972. Immunosuppression by the infectious bursal agent in chickens immunized against Newcastle disease. Vet. Rec., 90: 511-512. Billingham, R.E. and Medawar, P.B., 1951. The technique of free skin grafting in mammals. J. Exp. Biol., 28: 385--402. Cheville, N.F., 1967. Studies on the pathogenesis of Gumboro disease in bursa of Fabricius, spleen, and thymus of the chicken. Am. J. Pathol., 51: 527--539. Cho, B.R., 1970. Experimental dual infection of chickens with infectious bursal and Marek's disease agents. I. Preliminary observation on the effect of infectious bursal agent on Marek's disease. Avian Dis., 14: 665--675.
387 Cooper, M.D., Cain, W.A., Van Alten, P.J. and Good, R.A., 1969. Development and function of immunoglobulin producing system. I. Effect of bursectomy at different stages of development on germinal centers, plasma cells, immunoglobulins and antibody production. Int. Arch. Allergy, 35: 242--252. Faragher, J.T., Allan, W.H. and Cullen, G.A., 1972. Immunosuppressive effect of the infectious bursal agent in the chicken. Nature New Biol., 237: 118--119. Faragher, J.T., Allan, W.H. and Wyeth, P.J., 1974. Immunosuppressive effect of infectious bursal disease agent of vaccination against Newcastle disease. Vet. Rec., 95: 385--388. Giambrone, J.J., Eidson, C.S., Page, R.K., Fletcher, O.J., Barger, B.O. and Kleven, S.H., 1976. Effect of infectious bursal agent of the response of chickens to Newcastle disease and Marek's disease vaccination. Avian Dis., 20: 534--544. Giambrone, J.J., Eidson, C.S. and Kleven, S.H., 1977a. Effect of infectious bursal disease on the response of chickens to Mycoplasma synoviae, Newcastle disease virus and infectious bronchitis virus. Am. J. Vet. Res., 38: 251--253. Giambrone, J.J., Donahoe, J.P., Dawe, D.L. and Eidson, C.S., 1977b. Specific suppression of bursa-dependent immune system of chicks with infectious bursal disease virus. Am. J. Vet. Res., 38: 581--583. Gleason, R.E. and Fanguy, R.C., 1964. The relationship of blood groups to skin graft survival in chickens. Transplantation, 2: 509--514. Helmboldt, C.F. and Garner, E., 1964. Experimentally induced Gumboro disease (IBA). Avian Dis., 8: 561--575. Hudson, L., Pattison, M. and Thantrey, N., 1975. Specific B lymphocyte suppression by infectious bursal agent (Gumboro disease virus) in chickens. Eur. J. Immunol., 5: 675--679. Ivanyi, J., 1973. Sequential recruitment of antibody class-committed B lymphocytes during ontogeny. Eur. J. Immunol., 3: 789--793. Ivanyi, J., 1975. Immunodeficiency in chickens. I. Disparity in suppression of antibody responses to various antigens following surgical bursectomy. Immunology, 28: 1007-1013. Ivanyi, J. and Morris, R., 1976. Immunodeficiency in the chicken. IV. An immunological study of infectious bursal disease. Clin. Exp. Immunol., 23: 154--165. Wyeth, P.J., 1975. Effect of infectious bursal disease on the response of chickens to S. typhimurium and E. coli infections. Vet. Rec., 96: 2 3 8 - 2 4 3 .
383
Short Communication H U M O R A L AND C E L L - M E D I A T E D IMMUNE RESPONSES IN CHICKENS WITH INFECTIOUS BURSAL DISEASE
B. PANIGRAHY', L.K. MISRA2 and L.G. ADAMS 3 Departments of'Veterinary Microbiology, and 2Veterinary Pathology, College of Veterinary Medicine, Texas A & M University, College Station, TX 77843 (U.S.A.) 3Texas Agricultural Experiment Station, College Station, TX 77843 (U.S.A.)
(Accepted 15 April 1982)
ABSTRACT
Panigrahy, B., Misra, L.K. and Adams, L.G., 1982. Humoral and cell-mediated immune responses in chickens with infectious bursal disease. Vet. MicrobioL, 7: 383--387. Primary and secondary immune responses to Newcastle disease virus (NDV) was evaluated in chickens infected with infectious bursal disease virus (IBDV) at one and 28 days of age. The geometric mean primary hemagglutination-inhibition antibody titers (GMT) of chickens infected with IBDV at one day of age was significantly lower (P < 0.01) than those infected at 28 days of age. Infection with IBDV had no influence on secondary immune response to NDV. The effect of IBDV infection at one day of age on the cell-mediated immunity of chickens was evaluated by skin allograft acceptance or survival time. There was no significant difference between the percentage of grafts accepted in IBDV infected and noninfeeted control chickens. However, the mean graft survival time in the IBDV infected chickens was significantly longer (P ~< 0.05) than those in the control group. This suggested a suppression of cell-mediated immunity due to IBDV infection.
INTRODUCTION I n f e c t i o u s bursal disease (IBD) is a n a t u r a l l y o c c u r r i n g , virus-induced imm u n e d e f i c i e n c y o f c h i c k e n s c h a r a c t e r i z e d b y necrosis a n d d e p l e t i o n o f l y m p h o i d e l e m e n t s o f the b u r s a o f Fabricius. T h e b u r s a seeds B cell (bursad e p e n d e n t l y m p h o c y t e ) clones t o peripheral l y m p h o i d tissues d u r i n g emb r y o n a t i o n a n d t h e first f e w d a y s o f life. I n f e c t i o n o f chicks w i t h t h e inf e c t i o u s bursal disease virus ( I B D V ) at this t i m e has been s h o w n t o suppress h u m o r a l i m m u n e responses t o various antigens (Cho, 1 9 7 0 ; Allan et al., 1 9 7 2 ; F a r a g h e r et al., 1 9 7 2 , 1 9 7 4 ; H u d s o n et al., 1 9 7 5 ; W y e t h , 1 9 7 5 ; I v a n y i and Morris, 1 9 7 6 ; G i a m b r o n e et al., 1 9 7 6 , 1 9 7 7 a , b). O n t h e o t h e r h a n d , in i m m u n o l o g i c a l l y m a t u r e c h i c k e n s , i.e., at 28 d a y s o f age, I B D m a y p r o d u c e o n l y a partial o r n o i m m u n e suppression. I n a d d i t i o n t o l y m p h o i d d e g e n e r a t i o n o f t h e bursa, I B D V causes m o d e r a t e
0378-1135/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company
384 to severe lymphoid necrosis of the thymus and the spleen (Helmboldt and Garner, 1964; Cheville, 1967). The T cells (thymus-dependent lymphocytes) play a direct role in cell-mediated immunity. It can be postulated that the IBDV infection would interfere with immune reactions dependent on both the bursa and the thymus. The purpose of this study was to evaluate: (a) the effect of IBDV infection at one and 28 days of age on primary and secondary humoral immune response to Newcastle disease virus (NDV); and (b) cell-mediated immune response by skin aUograft survival in chickens infected at one day of age. MATERIALS AND METHODS
Stock IBDV. Bursal tissue from chickens naturally infected with IBDV was passaged once in 4-week-old susceptible chickens. The spleens were collected four days after infection. A 10% (w/v) spleen suspension in Hanks' balanced salt solution was prepared and assayed in 10-day-old specific pathogen free (SPAFAS Inc., Norwich, CT 06360} chicken embryos by the choriollantoic membrane route of inoculation. The titer of IBDV was 103.4 ELDs0/ml of the suspension. Chickens. One-day-old male White Leghorn chicks, free of demonstrable maternal antibody to IBDV by the agar gel precipitin test, were obtained from a commercial hatchery. These are non-inbred chicks from an incross line developed from mating of four inbred populations. Humoral immunity. Day-old chicks were distributed into three groups of 15 chicks each. Group 1 chicks served as noninfected controls. Chicks in groups 2 and 3 were infected with IBDV, respectively, at one and 28 days of age. Each chick was infected by conjunctival (one drop in each eye) and oral (0.2 ml) inoculation of the infectious spleen suspension. At 32 days of age, chickens in each group were immunized with NDV (B1 strain; titer, 104.2 TCIDs0/0.1 ml) by the conjunctival (one drop in each eye) route. Individual blood sera were collected 14 days following immunization and, at this time, each chick was reimmunized with NDV as before. Seven day s after the second immunization, individual blood serum samples were collected. The primary and secondary hemagglutination-inhibition (HI) antibody titers were measured by microtiter method. Statistical analysis of geometric mean HI antibody titers (GMT) was done by analysis of variance and Duncan's multiple-range test. Cell-mediated immunity. Day-old chicks were randomly distributed into t w o groups. One group of 50 chicks served as noninfected controls. Another group of 55 chicks was infected with IBDV at one day of age as previously described. At 5 days of age the chicks in each group received skin allografts. The donors and recipients were selected at random. Skin grafting was done
385 according to the techniques of Billingham and Medawar (1951) as modified by Gleason and Fanguy (1964). Grafts were examined for rejection or acceptance twice weekly for 10 weeks. Feather growth over the transplanted skin through the 10-week observation period was regarded as acceptance of the graft. On the other hand, formation of a scab followed by sloughing of skin was considered as the end point of graft rejection. Statistical analysis of skin graft survival was done by the Chi-Square method and the Student's t-test. RESULTS AND DISCUSSION
Humoral immunity. The primary GMT for NDV (Table I) in the noninfected control chickens and those infected with IBDV at one and 28 days of age, respectively, was 36.44, 10.08, and 20.74. Chickens infected at one day of age had significantly less (P < 0.01) GMT than the controls and those infected at 28 days of age. There was no significant difference in GMT in the latter two groups. Seeding of B cell clones to the peripheral lymphoid tissues occurs during e m b r y o n a t i o n and the first days of life (Cooper et al., 1969; Ivanyi, 1973, 1975). Therefore, it m a y be assumed that IBDV infection in ovo or on the day of hatching would result in suppression of humoral immune response. However, at 28 days of age, the chickens is immunologically mature, and infection with IBDV at this age would cause only a transient immunosuppression. The results of the present study and those of others (Faragher et al., 1972; Allan et al., 1972; Giambrone et al., 1976, 1977a) concur with these assumptions. The secondary GMT to NDV in control chickens and those infected with IBDV at one and 28 days of age, respectively, were 48.50, 38.50, and 36.15. These values were n o t significantly different. Although IBDV infection at one day of age caused a suppression of primary immune response to NDV, there was no suppression of the secondary immune response. Therefore, immune suppression because of IBDV infection as early as one day of age is n o t an irreversible process. TABLE I G e o m e t r i c m e a n primary and s e c o n d a r y h e m a g g l u t i n a t i o n - i n h i b i t i o n a n t i b o d y titers (GMT) to N e w c a s t l e disease virus in c h i c k e n s infected w i t h infectious bursal disease virus ( I B D V ) at one and 28 d a y s o f age Treatment
groups
N o n i n f e c t e d control I B D V i n f e c t i o n at one day o f age I B D V i n f e c t i o n at 28 d a y s of age
No. of chickens Primary GMT
S e c o n d a r y GMT
15
3 6 . 4 4 a*
48.50 a
15
10.08 b
38.50 a
15
20.74 a
36.15 a
*Values in each c o l u m n d e n o t e d b y different letters are significantly different at P ~<0.01 level.
386
Cell-mediated immunity. Results on the prolongation of skin graft survival in infected and noninfected chickens are presented in Table II. Twenty-eight of 55 (51%) of the infected and 19 of 50 (38%) of the noninfected birds accepted skin allografts. All chickens that accepted grafts had normal feather development. Although the percentage of chickens accepting the grafts was higher in the infected than in the noninfected group, the difference was n o t statistically significant. However, the mean graft survival time in the IBDVinfected group was significantly (P ~< 0.05) longer (48.07 days) than in the noninfected group (36.26 days). Prolonged skin graft survival in chickens infected at one day of age may be attributed to a suppression of cell-mediated immunity. TABLEII Prolongation of skin allograft survival in chickens infected with infectious bursal disease virus (IBDV) Treatment groups
No. of chickens grafted
No. of chickens accepting grafts
Percent graft acceptance
Mean graft survival time (days)
Noninfected control IBDV infection at one day of age
50
19
38 a*
36.26 a
55
28
51 a
48.07 b
*Values in each column denoted by different letters are significantly different at P ~< 0.05 level.
In conclusion, chickens infected with IBDV at one day of age had significantly lower (P ~< 0.01) antibody titers to NDV than the chickens infected at 28 days of age. However, the immunosuppressive effect of IBDV on the secondary immune response was n o t observed. Prolonged skin graft survival in chickens infected at one day of age suggested suppression of cell-mediated immunity.
REFERENCES Allan, W.H., Faragher, J.T. and Cullen, G.A., 1972. Immunosuppression by the infectious bursal agent in chickens immunized against Newcastle disease. Vet. Rec., 90: 511-512. Billingham, R.E. and Medawar, P.B., 1951. The technique of free skin grafting in mammals. J. Exp. Biol., 28: 385--402. Cheville, N.F., 1967. Studies on the pathogenesis of Gumboro disease in bursa of Fabricius, spleen, and thymus of the chicken. Am. J. Pathol., 51: 527--539. Cho, B.R., 1970. Experimental dual infection of chickens with infectious bursal and Marek's disease agents. I. Preliminary observation on the effect of infectious bursal agent on Marek's disease. Avian Dis., 14: 665--675.
387 Cooper, M.D., Cain, W.A., Van Alten, P.J. and Good, R.A., 1969. Development and function of immunoglobulin producing system. I. Effect of bursectomy at different stages of development on germinal centers, plasma cells, immunoglobulins and antibody production. Int. Arch. Allergy, 35: 242--252. Faragher, J.T., Allan, W.H. and Cullen, G.A., 1972. Immunosuppressive effect of the infectious bursal agent in the chicken. Nature New Biol., 237: 118--119. Faragher, J.T., Allan, W.H. and Wyeth, P.J., 1974. Immunosuppressive effect of infectious bursal disease agent of vaccination against Newcastle disease. Vet. Rec., 95: 385--388. Giambrone, J.J., Eidson, C.S., Page, R.K., Fletcher, O.J., Barger, B.O. and Kleven, S.H., 1976. Effect of infectious bursal agent of the response of chickens to Newcastle disease and Marek's disease vaccination. Avian Dis., 20: 534--544. Giambrone, J.J., Eidson, C.S. and Kleven, S.H., 1977a. Effect of infectious bursal disease on the response of chickens to Mycoplasma synoviae, Newcastle disease virus and infectious bronchitis virus. Am. J. Vet. Res., 38: 251--253. Giambrone, J.J., Donahoe, J.P., Dawe, D.L. and Eidson, C.S., 1977b. Specific suppression of bursa-dependent immune system of chicks with infectious bursal disease virus. Am. J. Vet. Res., 38: 581--583. Gleason, R.E. and Fanguy, R.C., 1964. The relationship of blood groups to skin graft survival in chickens. Transplantation, 2: 509--514. Helmboldt, C.F. and Garner, E., 1964. Experimentally induced Gumboro disease (IBA). Avian Dis., 8: 561--575. Hudson, L., Pattison, M. and Thantrey, N., 1975. Specific B lymphocyte suppression by infectious bursal agent (Gumboro disease virus) in chickens. Eur. J. Immunol., 5: 675--679. Ivanyi, J., 1973. Sequential recruitment of antibody class-committed B lymphocytes during ontogeny. Eur. J. Immunol., 3: 789--793. Ivanyi, J., 1975. Immunodeficiency in chickens. I. Disparity in suppression of antibody responses to various antigens following surgical bursectomy. Immunology, 28: 1007-1013. Ivanyi, J. and Morris, R., 1976. Immunodeficiency in the chicken. IV. An immunological study of infectious bursal disease. Clin. Exp. Immunol., 23: 154--165. Wyeth, P.J., 1975. Effect of infectious bursal disease on the response of chickens to S. typhimurium and E. coli infections. Vet. Rec., 96: 2 3 8 - 2 4 3 .