Mitogenic activity of purified capsular polysaccharide A from Bacteroides fragilis: differential stimulatory effect on mouse and rat lymphocytes in vitro.
Bacteroides fragilis, a Gram-negative colonic bacterium, induces the formation of abscesses associated with intra-abdominal sepsis in humans. The singular ability of this organism to modulate abscess formation in experimental rodent models resides in the structurally distinct and ionically charged capsular polysaccharides A (PS A) and B (PS B). The regulation of abscess formation in animals is dependent on T lymphocytes. However, the manner in which PS A interacts with T cells remains unknown. We therefore tested the T cell stimulatory capacity of purified PS A on mouse and rat lymphocytes in cellular proliferation assays and found that the PS A molecule possesses mitogenic characteristics distinguishable from those of the polyclonal B cell activator LPS, the T cell mitogen Con A, and staphylococcal enterotoxin A superantigen. Further, PS A stimulated proliferation of normal mouse and rat lymphocytes differentially. Mouse B cells responded to PS A in a fashion that did not require exogenous APC function, while rat T lymphocyte responses to PS A required APC function derived from autologous or xenogenic feeder cells. Cellular depletion experiments showed that the CD4+ subset of rat spleen cells was the primary responder cell type to PS A in vitro. The differential stimulatory effects of PS A on mouse and rat lymphocytes may reflect its ability to stimulate different lymphocyte subsets in vivo through the activities of receptor/counter-receptor pairs present on responder lymphocytes and cognate APC.
Brubaker
J O
JO
Laboratory of Infectious Diseases, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
Li
Q
Q
Tzianabos
A O
AO
Kasper
D L
DL
Finberg
R W
RW
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology* / Q000494:pharmacology; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology; D016667:Bacterial Capsules / Q000276:immunology* / Q000494:pharmacology; D001441:Bacteroides fragilis / Q000276:immunology*; D002455:Cell Division / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D016131:Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008934:Mitogens / Q000494:pharmacology*; D011135:Polysaccharides, Bacterial / Q000276:immunology* / Q000494:pharmacology; D051381:Rats; D011917:Rats, Inbred Lew; D017208:Rats, Wistar