T cell tolerance in the chicken. II. Lack of evidence for suppressor cells in tolerant agammaglobulinemic and normal chickens

Functional and biochemical characterizations of avian T lymphocyte antigens identified by monoclonal antibodies

Seven monoclonal antibodies (mAb) were used to characterize antigens present on chicken T lymphocytes and on natural killer cells by flow cytometry, radioimmunoprecipitation and by effects on cell-mediated cytotoxicity and mitogen-induced proliferation. mAb CTLA8 and 5 stained 73% of thymus, 44% of spleen and 51% of peripheral blood lymphocytes (PBL), respectively, and immunoprecipitated 65- and 45-kDa proteins from detergent extracts of 125I surface-labeled thymocytes. Pretreatment of splenic lymphocytes with mAb CTLA5 and 8 in the presence of rabbit complement (C) eliminated the concanavalin A (Con A)-induced T cell proliferative responses. mAb CTLA3, 4 and 9 stained 43% of thymus, 36% of spleen and 18% of PBL, and immunoprecipitated 33-35-kDa proteins. Pretreatment of spleen cells with mAb 4 or 9 plus C reduced, but did not eliminate, the Con A-induced proliferative response and significantly reduced both major histocompatibility complex (MHC)-restricted and non-MHC-restricted cellular cytotoxicity. mAb CTLA1 and 6 stained 58% of thymus, 13% of spleen and 19% of PBL. mAb CTLA1 and 6 immunoprecipitated a 65-kDa protein. mAb CTLA1 and 6 had no effect on the Con A-induced blastogenesis and CTLA6 caused no decrease in virus-specific cytotoxic T lymphocyte and natural killer activity. These results indicate that (a) mAb CTLA5 and 8 identify antigens on mature T lymphocytes that are similar in tissue distribution, molecular mass and function to the mammalian CD5 antigen; (b) mAb CTLA3, 4 and 9 detect the avian homologue of CD8 antigen; and (c) mAb CTLA1 and 6 identify the avian homologue of CD4 antigen.

Susceptibility to tolerance induction of bursal and peripheral B cells

We investigated cellular aspects of immunological tolerance to protein antigens in chickens by examining the immune responses of bursal and splenic cells from tolerant or normal chickens after transfer into cyclophosphamide (CP)-treated recipients. Newly-hatched chicks were made tolerant to bovine serum albumin (BSA) by injection of 100 mg of the antigen. When bursa cells from 4-day-old BSA-unresponsive chicks were transferred into CP-treated recipients, the reconstituted birds were able to respond to a subsequent injection of BSA almost as well as normal birds, and as well as CP-treated birds that had been reconstituted with normal bursa cells. To investigate whether the presence of the BSA antigen might affect recovery from tolerance, we injected CP-treated recipients with BSA at the time of transfer of bursal cells. The presence of the antigen prevented the recovery of the anti-BSA response in reconstituted birds. When spleen cells from 6.5-week-old unresponsive chicks were transferred into CP-treated recipients, no recovery of responsiveness to BSA could be demonstrated. A likely reason for the failure of splenic B cells to recover responsiveness on transfer is their inability to generate somatic variants of Ig genes in the same way as bursal stem cells. Thus, when the bursa involutes, the chicken's antibody repertoire may be frozen in a less adaptable state than that of a mammal.

Suppressor T cells with histamine type II receptors in chickens bearing chemically induced fibrosarcomas

Immunity to a local (wing web) challenge with transplantable, chemically induced tumors, such as CHCT-NYU-4, can be transferred to histocompatible SC chickens with intravenously injected splenic T cells from tumor-immune chickens. Simultaneous iv injection of splenic T cells from chickens bearing progressively growing CHCT-NYU-4 prevents the expression of this adoptive systemic tumor immunity. The splenic suppressor T cells are B-L(Ia) positive and adhere to dishes coated with cimetidine-protein conjugate, suggesting that they bear type II histamine receptors (H2R). Intravenous injection of gamma-irradiated CHCT-NYU-4 cells 7 days prior to a local challenge with the same tumor promotes growth of a normally suboptimal tumor cell dose such that the incidence of progressive tumor growth is significantly increased. Concomitant treatment with the H2R antagonist, ranitidine, inhibits tumor growth of an optimal tumor dose challenge and promotes induction of tumor immunity. However, this drug cannot reverse the effect of iv injected tumor cells. Another drug with reported antisuppressor cell activity, cyclophosphamide (50 mg/kg), injected 1 day prior to challenge causes a transient inhibition of tumor growth. Injection of this drug on Day 7 does not have a significant effect by itself but, in combination with the Day-1 pretreatment, a significant inhibition of tumor growth by size and tumor incidence measurements is obtained. These results indicate that manipulation of immunity to transplantable fibrosarcomas in the chicken is possible with drugs acting on suppressor cells.

Chickens bursectomized with mibolerone have Ig-positive cells which lack bursal cell specific antigens

The bursa anlage failed to develop in chicken embryos injected with 5 micrograms mibolerone on the 5th day of embryonation. Humoral immune responses in treated birds were studied by challenging them with sheep red blood cells (SRBC) and killed Brucella abortus (B. abortus) at 4, 5, 6 and 7 weeks of age. Control birds responded with IgM and IgG titers to SRBC and B. abortus, whereas mibolerone-treated birds completely failed to respond to B. abortus and their responses to SRBC consisted of only IgM agglutinins. Mibolerone-treated birds lacked natural agglutinins to rabbit red blood cells. The total concentration of plasma IgG, measured by radial immunodiffusion, was diminished whereas the IgM level was not influenced by the mibolerone treatment. Mibolerone-treated birds lacked bursal cell specific antigens in the peripheral blood leucocytes (PBL) but they still had Ig-positive fluorescing cells which were fewer in number than those of controls. Splenomegaly resulting from graft vs. host reactions induced in chick embryos by PBL from mibolerone-treated birds was similar to that in control birds, indicating normal alloreactive T cells. These results suggest that IgM responses observed in mibolerone-treated birds are produced by cells from an extrabursal site, and that mibolerone can be used effectively to chemically bursectomize chickens.

The effects of in ovo mibolerone treatment on the bursa of Fabricius and the humoral system of chickens: a dose-response study

The effects of various doses of mibolerone, an analog of testosterone, in the development of the bursa of Fabricius and the humoral immune system were examined by injecting 0.01, 0.1, 1, 10 or 100 micrograms mibolerone into the chorio-allantoic cavity of 12-day-old chick embryos. Treatment with 0.01 or 0.1 micrograms of mibolerone caused slight or no bursal atrophy, 1 microgram caused substantial bursal atrophy, and 10 or 100 micrograms caused severe bursal atrophy at the time of hatching and at 6 weeks of age. When mibolerone-treated birds were challenged with sheep red blood cells and killed Brucella abortus at 4 and 5 weeks of age, birds treated with 10 or 100 micrograms of mibolerone had suppressed humoral responses to sheep erythrocytes and B. abortus whereas birds treated with 0.01 and 0.1 micrograms of mibolerone had normal humoral immune responses. Birds treated with 1 microgram mibolerone had normal humoral immune responses to sheep erythrocytes and B. abortus (except for low IgG responses to B. abortus) despite the fact that the birds had substantially atrophic bursae during their embryonic and post-embryonic development. These results are discussed in relation to an earlier claim that mibolerone given in microgram quantities in feed during the post-hatch period causes rapid development of the humoral immune system.

Inherited dysgammaglobulinemia of chickens: reduced incidence of disease in parabiotic chimeras

University of California, Davis (UCD) line 140 chickens develop a dysgammaglobulinemia characterized as selective 7S immunoglobulin (Ig) deficiency with elevated serum IgM levels. To study the role of bursal development on the expression of dysgammaglobulinemia in these birds, we examined the effect of bursacyte transfer to line 140 birds and parabiosis between UCD 140 and a control line of chickens on changes in serum IgM and 7S Ig levels. Bursacyte transfer was performed by injecting 18-day UCD 140 embryos (which had been cyclophosphamide treated on Day 15) with bursacytes from major histocompatibility complex B-matched control line (11 X 58) F1 birds. This transfer produced little change in the incidence of dysgammaglobulinemia in UCD 140 transfer birds (56%) compared to unmanipulated line 140 birds (60%). These data reflect a failure of line 140, rather than technique, because successful reconstitution was seen using line 11 X 58 birds injected with 11 X 58 bursacytes. In contrast, the generation of UCD 140/line 11 X 58 chimeras significantly reduced the incidence of dysgammaglobulinemia in line UCD birds. Indeed, fusion of the chorioallantoic vascular system (parabiosis) of UCD 140 and 11 X 58 embryos on Day 15 decreased the frequency of dysgammaglobulinemia of UCD 140 parabionts to 14% compared to 66% in unmanipulated line 140 controls. The success of parabiosis was 83% as determined by demonstrating chimerism with allogeneic blood groups. Moreover, the frequency of dysgammaglobulinemia in the 17% of parabionts that did not reveal chimerism was similar to unmanipulated UCD 140 chickens.

Neonatal splenic suppressor cells in the chicken. I. In vivo suppression of the immune response to bovine serum albumin by normal and tolerized neonatal spleen cells

The presence of active splenic suppressor cells in neonatal chickens, either normal or tolerant to bovine serum albumin (BSA), was examined by assessment of their effect on both primary and adoptively transferred secondary responses to BSA or sheep red blood cells (SRC). Both normal and BSA tolerized spleen cells were shown to be highly suppressive of secondary anti-BSA responses generated by specifically primed adult spleen cells in inert recipients. Suppression of the secondary anti-BSA response by normal spleen cells was slightly less effective than that seen with BSA tolerant spleen cells. Transfer of BSA tolerant spleen cells into normal recipients, followed by BSA challenge, prevented any significant primary anti-BSA response. In contrast, transfer of normal spleen cells into normal recipients, followed by BSA challenge, failed to show any suppression of the resulting primary response. Neither normal nor BSA tolerant neonatal spleen cells were capable of suppressing either primary or secondary responses to SRC. Thus, chickens tolerized to BSA have suppressor cells specific for the tolerizing antigen. We present evidence that both the tolerance associated suppressors and the suppressors detected in normal neonatal chickens are T cells.

Studies on the immune response in chickens. IV. Generation of hapten-specific memory and absence of increase in carrier-specific helper memory in antibody response to sheep red blood cell antigen and its hapten-conjugate

The role of carrier recognition in the hapten-specific antibody response of chickens to hapten (TNP) conjugate of sheep red blood cells (SRBC) was studied. The anti-TNP antibody response to the challenge with either TNP-SRBC or DNP conjugate of Salmonella enteritidis (DNP-Sal) of chickens previously primed with TNP-SRBC was definitely higher than that of unprimed chickens. Injection of TNP-chicken red blood cells, which did not provoke any significant primary anti-TNP response, also induced the memory for secondary anti-TNP response to the challenge with TNP-SRBC or DNP-Sal. The TNP-specific memory generated by stimulation with TNP-SRBC was adoptively transferable by spleen cells into cyclophosphamide (CY)-treated X-irradiated syngeneic recipients. On the other hand, the SRBC-specific memory for augmentation of anti-TNP response to the challenge with TNP-SRBC was never detected in chickens previously primed with either any of a wide range of doses (10(4)-10(8)) of SRBC, solubilized SRBC or SRBC fixed with formaldehyde, nor in CY-treated X-irradiated chickens receiving SRBC-primed spleen cells. The anti-TNP response of chickens to the challenge with TNP-SRBC was rather suppressed by the SRBC preimmunization. The passively administered anti-SRBC chicken serum also suppressed the response to TNP-SRBC. The carrier-specific suppressor activity generated by SRBC stimulation was not adoptively transferable by spleen cells. It is suggested from these results that the mechanism of amplification of the anti-hapten antibody response of chickens to hapten-SRBC conjugate is primarily mediated by the hapten-recognition, and carrier-recognition is more important for suppression rather than for amplification of the anti-hapten response, although the inductive mechanism for anti-hapten response itself should somehow involve the carrier recognition.

Enhancing effect of surgical bursectomy on antibody response

Effect of surgical bursectomy on antibody response was studied in chicks injected intrabursally with sheep red blood cells (SRBC) and Brucella abortus on day 2 of life and challenged intravenously with the same antigens on day 9. Bursectomy performed 2 days after the priming resulted in a significantly decreased anti-SRBC plaque-forming cell (PFC) response, whereas bursectomy performed 4 or 5 days after the priming clearly enhanced the PFC response. The enhancing effect of bursectomy on the PFC response was also observed if the priming was made intravenously. In antibody titers against SRBC the enhancing effect was observed only if a secondary and tertiary challenge was performed at the age of 28 and 36 days, respectively. Titers of Brucella antibodies were either reduced by the bursectomy (performed 2 or 4 days after the intrabursal priming) or left unaffected (bursectomy performed 5 days after the priming). These findings are discussed in relation to bursa-derived suppressor cells.