The autoantigenic response to rabbit cytochrome c

The immune response to cytochrome c in BALB/c mice is delayed due to inability of their non-specific antigen-presenting cells to provide its immunodominant epitope

The antibody response to horse cytochrome c (cyt.c) in BALB/c mice developed slowly and a substantial production of IgG antibodies was observed only 26-30 days after immunization. Lymph node cells (LNC) of unimmunized mice proliferated weakly in response to both native cyt.c and its synthetic peptides. On day 8 after immunization, LNC could not be stimulated with native cyt.c and peptide 92-104. However, they did proliferate in response to cyt.c peptides 1-6, 1-13, 2-13, 14-22, 46-56, 57-77, 61-77 and 61-69 which are closely related in horse and mouse cyt.c. On day 26, both native cyt.c and the peptides, including 92-104, were equally active in stimulating LNC proliferation. Both plastic-adherent and cyt.c-specific cells panned from day 8 cells enhanced the response of unprimed cells to native cyt.c. Elimination of B cells demonstrated that primary recognition of cyt.c was mediated, at least partly, by non-specific antigen-presenting cells (APC) while later B cells of additional specificities were involved. It is concluded that immunization with horse cyt.c initiated an autoimmune response resulting in T-dependent anergy. Peptide determinants processed by non-specific APC stimulated corresponding autoreactive T cells. Specific B cells which appeared as a result of the response maturation processed successfully the immunodominant epitope and finally mediated proliferative and antibody responses.

Interrelating B cell subpopulations and environmental regulation with the expression of three tiers of repertoire diversity

The B cell repertoire consists of three tiers of clonotype diversity. One tier, which is the product of H chain V region rearrangements in the absence of N additions, is of limited diversity (less than 10(8) clonotypes) so that clonotypes of this tier would be expected to recur within and among B cells of individuals of an inbred strain. These clonotypes, therefore, could be subjected to, and conserved by, evolutionary selective pressures such as those imposed by ubiquitous bacterial pathogens. The second tier of clonotypes is created by H chain V region rearrangements that include N additions, and is, therefore, exceedingly diverse. Clonotypes of this tier would be unlikely to recur; however, by providing maximal diversity they would ensure protection against a wide spectrum of pathogens. The third tier of diversity is that which is generated by the superimposition of somatic mutations on clonotypes of the other two tiers. This tier of clonotypes is reflective of the refinement of specificities that are destined for expression in memory B cells. B cells exists as three distinct subpopulations, Ly-1 B cells, conventional primary B cells and memory B cells. These subpopulations differ functionally, developmentally, and by the extent to which they are impacted by immunoregulatory processes. Furthermore, B cells of these subpopulations differentially express the three tiers of clonotype diversity.