In vitro activation of murine antigen-specific memory B cells by a T-dependent antigen.
A procedure that generates an enriched population (60 to 85%) of memory B cells specific for TNP (TNP-MABC) was employed. The activation requirements of TNP-MABC for the T-dependent antigen TNP-KLH and carrier-primed helper T (Th) cells were compared to those for TNP-binding cells from nonimmune mice (TNP-ABC). Proliferation and differentiation of TNP-MABC in response to cognate recognition of antigen requires less antigen and fewer carrier-primed Th cells than the activation of TNP-ABC. Furthermore, responses of the TNP-MABC were of a greater magnitude. Non-cognate activation induces a low level of proliferation of both TNP-ABC and TNP-MABC, but induces differentiation of TNP-MABC only. Percoll density fractionation of spleen cells prior to enrichment for TNP-MABC suggests that the small, dense cell population responds to cognate, but not to non-cognate activation. FACS separation of TNP-MABC by surface Ig isotype reveals that approximately 80% of the secondary IgG response is derived from cells expressing sIgG. Such cells constitute less than 10% of the total number of TNP-MABC. Limiting dilution studies with sorted TNP-MABC indicate that sIgG+ TNP-MABC are enriched for precursors that give rise to a large clone size. The in vitro results indicate the existence of three putative pathways for antigen-specific memory B cell activation by a T-dependent antigen: 1) sIgG+ cells differentiating into IgG-secreting cells; 2) sIgM+ cells differentiating into IgG-secreting cells; and 3) sIgM+ cells differentiating into IgM-secreting cells.
E
E
Yefenof
V M
VM
Sanders
J W
JW
Uhr
E S
ES
Vitetta
D000818:Animals; D001402:B-Lymphocytes / Q000145:classification / Q000276:immunology* / Q000378:metabolism; D001666:Binding Sites, Antibody; D002352:Carrier Proteins / Q000276:immunology; D002469:Cell Separation; D000939:Epitopes / Q000276:immunology; D005260:Female; D006241:Haptens / Q000276:immunology*; D006433:Hemocyanins / Q000276:immunology; D007074:Immunoglobulin G / Q000032:analysis / Q000096:biosynthesis; D007156:Immunologic Memory; D007958:Leukocyte Count; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D013601:T-Lymphocytes / Q000276:immunology*; D014301:Trinitrobenzenes / Q000276:immunology
D002352:Carrier Proteins; D000939:Epitopes; D006241:Haptens; D007074:Immunoglobulin G; D014301:Trinitrobenzenes; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin