title: Autonomous activation of B and T cells in antigen-free mice.
abstract: The spleen of adult antigen-free mice contains a sizable proportion (5-15%) of activated cells in all lymphocyte sets, as marked by the membrane expression of immunoglobulins, L3T4 and Lyt-2 antigens. The frequency of activated cells is very high in early post-natal life, and reaches adult levels by 6 weeks of age when it is comparable to that observed in healthy unmanipulated mice raised in conventional conditions. The effector B cell compartment is quantitatively similar in antigen-free mice and specific pathogen-free mice, but the former is deficient in isotype diversification, since IgG- and IgA-secreting cells are drastically reduced. The effector T cell compartment is slightly reduced in number, but is equally competent in providing help or suppression of syngeneic B cells. The results indicate the existence of a compartment of the immune system displaying autonomous self-determined activity which is predominant early in life. This compartment, physically localized to the spleen, appears to be distinct from an antigen-dependent compartment which is essential for the development of peripheral lymphoid organs draining sites of "natural" environmental immunization.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000145:classification / Q000276:immunology*; D005856:Germ-Free Life; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D013047:Specific Pathogen-Free Organisms; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*