The thymus‐independent antigen α(1–3) dextran elicits proliferation of precursors for specific IgM antibody‐producing cells (memory cells), which are revealed by LPS stimulation in soft agar cultures and detected by immunoblot

摘要

AbstractSingle antibody‐forming cells (AFC) specific for α(l‐3) dextran (Dex) from i.p.‐immunized BALB/c mice were enumerated in soft agar cultures by blotting on antigen‐precoated membranes and subsequent staining via enzyme‐coupled anti‐IgM antibodies. Short cultures (2 h) revealed AFC as harvestedex vivo, while in long‐term cultures (4 days), in the presence of lipopolysaccharide (LPS) as B cell mitogen, cells or colonies developed by differentiationin vitro. Whereas the spleen contained most AFCex vivoin a sharp‐peak response at 4 and 5 days after i.p. injection of Dex in aqueous solution, peritoneal exudate cells (PEC) contained only very few AFC. However, the same PEC population developed Dex‐specific cells or colonies after 4 days of culture. The isotype of antibodies was IgM. The frequency of these Dex‐specific LPS‐inducible precursor cells rose exponentially in the course of the immune response to a broad plateau and was still, 11 weeks after Dex injection, approximately 40‐fold higher than in non‐immunized mice.Since these cells increased in frequency after antigen injection, and since they could not be detected as AFC during 2 hex vivo, they were regarded as memory cells. They seemed to be arrestedin vivo, but could be induced to differentiation and/or proliferationin vitro. Although these cells had the functional characteristics of memory cells as defined above, they produced anti‐Dex antibodies of IgM isotype. Their population might be critical for the protection of the peritoneal cavity against microbial invasion from the intestines, and it may be significant in this context that we could evoke a peritoneal memory cell response only when antigen was injected intraperitoneally, but not intravenously. In athymic BALB/c‐nu/nu mice only few of these Dex‐specific memory cells were found. It is possible that T cells exert a regulatory influence on