title: Microbial induction of co-stimulatory activity for CD4 T-cell growth.
abstract: The activation of naive CD4 T cells by antigen is a critical step in the initiation of an immune response; it requires both ligation of the T-cell receptor (TCR) and the delivery of co-stimulatory factors by accessory cells. We have examined the role of syngeneic accessory cells in the response of purified normal CD4 T cells to anti-CD3 antibody as ligand. We show that the ability to deliver co-stimulatory signals is inducible in B cells by microbial products such as bacterial lipopolysaccharide (LPS), mitogenic influenza viruses, and synthetic polyinosinic-polycytidylic acid (poly-I:C) as a mimic of viral infection. LPS stimulation for 16 h allows the co-stimulatory activity of B cells to become resistant to paraformaldehyde fixation. LPS induction of fixation-resistant co-stimulator activity requires new protein synthesis, as it is inhibited by cycloheximide. Using the anti-CD45RB mAb 16A as marker for naive and memory CD4 T cells, we show that B cells activated by LPS and by poly-I:C can provide co-stimulatory signal to both naive and memory CD4 T cells. By contrast, zymosan particles, which are known to activate macrophages in a variety of assays, do not activate B cells to become co-stimulatory, but do induce this activity in macrophages. These data demonstrate that a variety of infectious agents or their constituents can induce accessory cells to become co-stimulatory for CD4 T cells. They are interpreted in light of a proposed role for two classes of recognition in the induction of the immune responses, specific recognition of antigens and non-specific recognition of infectious agents. These data support the contention that the immune system uses this mechanism to discriminate infectious non-self from non-infectious self.
authors.affiliation: Section of Immunobiology, Yale University School of Medicine, New Haven, CT.
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: C A
authors.initials: CA
authors.lastname: Janeway
mesh_terms: D000818:Animals; D000906:Antibodies; D000938:Antigen-Presenting Cells / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte; D001402:B-Lymphocytes / Q000276:immunology; D017252:CD3 Complex; D015704:CD4 Antigens; D007156:Immunologic Memory; D066298:In Vitro Techniques; D009980:Influenza A virus / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology; D051379:Mice; D011070:Poly I-C / Q000494:pharmacology; D011948:Receptors, Antigen, T-Cell; D011961:Receptors, Fc; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*
chemical_list: D000906:Antibodies; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015704:CD4 Antigens; D008070:Lipopolysaccharides; D011948:Receptors, Antigen, T-Cell; D011961:Receptors, Fc; D011070:Poly I-C