THE ROLE OF VARIOUS COMPARTMENTS IN THE CHICKEN SPLEEN DURING AN ANTIGEN-SPECIFIC HUMORAL RESPONSE

In the chicken spleen, certain aspects of the complex of ellipsoid, pe ri-ellipsoid lymphocyte sheath (PELS), and ring of macrophages are mor phologically and functionally similar to the marginal zone in the mamm alian spleen. In this study, the role of this marginal zone-like compl ex was examined during the humoral immune response against a thymus-de pendent antigen. The antigen peroxidase-conjugated rabbit anti-peroxid ase (PAP) was injected intravenously in chickens and subsequently visu alized by its enzymatic activity. Anti-PAP antibody-containing cells ( ACC) were detected by incubation with PAP and subsequent peroxidase st aining. Shortly after injection, PAP antigen was located in the ellips oids. Within 24 hr most PAP had relocated to the B lymphocytes of the PELS. After this, most PAP disappeared, although minute amounts of PAP were detected in peri-arteriolar T-cell areas (PALS). At 48 hr, the P ALS contained the first anti-PAP ACC; later ACC were also located in t he red pulp. During the immune response, the isotype of the ACC switch ed from IgM to IgG. From 72 hr, PAP antigen and anti-PAP antibodies we re trapped on follicular dendritic cells in immature and mature germin al centres. These results demonstrate that humoral immune responses ar e induced by the interaction of the PALS and the complex of ellipsoid, PELS and macrophages. These results, along with earlier ones, suggest that this complex is analogous to the marginal zone in the mammalian spleen.