In Vitro Growth and Differentiation of Rat B Cell Subpopulations

Abstract

In previous studies we have shown the existence of at least two subpopulations of B lymphocytes in rabbit spleen, different in size, morphology and redistribution behaviour of their surface immunoglobulin (sIg). One of these subsets consists of medium-sized lymphocytes that form caps with anti-immunoglobulin antibodies. The other subset consists of small lymphocytes that do not form sIg-caps, but show rapid endocytosis in the cap configuration 1,2. Bazin et al. ³ and Gray et al. ⁴ showed in rat spleen that marginal zone lymphocytes carry sIgM but no sIgD, while the small B lymphocytes in the corona of the follicles carry both sIgM and sIgD. In preliminary studies with rats, we have found analogies with our previous work with rabbits, i.e. sIgM could be brought to cap formation in about one half of the B cell population, while sIgD could not be found in caps to a considerable amount and disappeared rapidly from the cell surface, presumably by endocytosis. In the present study we have tried to separate both subsets to study their responsiveness to B cell mitogens in vitro.