Correlation between specific immunosuppression and polyclonal B cell activation induced by a protein secreted by Streptococcus mutans.
The relationship between polyclonal B cell activation and immunosuppressor effects induced by F5'EP-Sm, a non-cytotoxic protein secreted by Streptococcus mutans, was studied in C57BL/6 mice. Mice treated with F5'EP-Sm exhibited a considerable increase in splenic nonspecific Ig plaque-forming cells (PFC) compared with untreated mice. The isotypic pattern of non-specific PFC responses favours IgG2a approximately equal to IgG2b greater than IgG3 greater than IgG1 approximately equal to IgM, when taken as a ratio between treated and untreated animals. When F5'EP-Sm was administered 2 days before immunization with sheep red blood cells (SRBC), the non-specific PFC production was accompanied by an ephemeral increase in specific PFC against SRBC 1 day after immunization, which was quickly replaced by a strong immunosuppression. In contrast, when F5'EP-Sm was injected after priming, there was little or no demonstrable suppression of specific PFC, and the increase of non-specific PFC was much less evident. The kinetic curves representing increase or decrease in relation to controls of specific and non-specific PFC are almost mirror images in each of the isotypes. The in vivo suppressor effect was abrogated in thymectomized mice, although the involvement of the T cell compartment is probably secondary to the B cell mitogen effect, since T-depleted spleen cells proliferate and synthesize non-specific Ig when stimulated in vitro with F5'EP-Sm.
Ferreira
P
P
Department of Immunology, Institute for Biomedical Sciences Abel Salazar, Porto, Portugal.
Soares
R
R
Ribeiro
A
A
Arala-Chaves
M
M
D000818:Animals; D000917:Antibody Formation / Q000187:drug effects; D001402:B-Lymphocytes / Q000276:immunology*; D001426:Bacterial Proteins / Q000276:immunology* / Q000494:pharmacology; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D013295:Streptococcus mutans / Q000276:immunology*; D013491:Suppressor Factors, Immunologic / Q000276:immunology*; D013934:Thymectomy
D001426:Bacterial Proteins; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D013491:Suppressor Factors, Immunologic