Identification of a novel surface protein on activated CD4+ T cells that induces contact-dependent B cell differentiation (help).
CD4+ T lymphocytes provide contact-dependent stimuli to B cells that are critical for the generation of specific antibody responses in a process termed T helper function. The surface structures on activated CD4+ T cells that mediate this function are not fully known. We previously reported the isolation of a functionally unique subclone of the Jurkat leukemic T cell line (D1.1) that constitutively expressed contact-dependent helper effector function. To identify T cell surface molecules that mediate contact-dependent T helper function, a monoclonal antibody (mAb), designated 5c8, was generated that inhibits D1.1-mediated B cell activation and immunoprecipitates a novel 30-kD protein structure from surface-iodinated D1.1 cells. Normal CD4+ T cells express 5c8 antigen (Ag) transiently 5-6 h after activation by phorbol myristate acetate and phytohemagglutinin with maximal expression 5-6 h after activation and absence of expression by 24 h. In contrast, neither resting nor activated CD8+ T cells express 5c8 Ag. In functional studies, mAb 5c8 inhibits the ability of fixed, activated CD4+ T cells to induce B cell surface CD23 expression. In addition, mAb 5c8 inhibits the ability of CD4+ T cells to direct terminal B cell differentiation driven by pokeweed mitogen. Taken together, these data suggest that 5c8 Ag is a novel, activation-induced surface T cell protein that is involved in mediating a contact-dependent element of the helper effector function of CD4+ T lymphocytes.
Department of Medicine, Columbia University, New York, New York 10032.
S
S
Lederman
M J
MJ
Yellin
A
A
Krichevsky
J
J
Belko
J J
JJ
Lee
L
L
Chess
D000911:Antibodies, Monoclonal / Q000276:immunology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis; D000954:Antigens, Surface / Q000502:physiology*; D001402:B-Lymphocytes / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D016827:CD8 Antigens / Q000032:analysis; D002448:Cell Adhesion; D002450:Cell Communication; D002454:Cell Differentiation; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D011233:Precipitin Tests; D011961:Receptors, Fc / Q000032:analysis; D017455:Receptors, IgE; D016176:T-Lymphocyte Subsets / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D000954:Antigens, Surface; D016827:CD8 Antigens; D011961:Receptors, Fc; D017455:Receptors, IgE