Resting and anergic B cells are defective in CD28-dependent costimulation of naive CD4+ T cells.
Successful antibody production in vivo depends on a number of cellular events, one of the most important of these being cognate B cell-T cell interaction. To examine this phenomenon in vitro, homogeneous populations of hen egg lysozyme (HEL)-specific small resting B cells and naive CD4+ HEL-specific T cells (derived from immunoglobulin [Ig] and T cell receptor transgenic mice, respectively) were cultured together. On addition of intact HEL protein. HEL-specific B cells increase their expression of activation molecules, including a B7-related protein and CD44, and enlarge into blast cells. Within the same cultures, HEL-specific CD4+ T cells also increase expression of the activation markers CD69 and CD44, enlarge, secrete lymphokines, and proliferate. This response is radiation sensitive, supporting the conclusion that HEL-specific B cells present antigen to and activate the naive T cells. By contrast, when a synthetic peptide fragment of HEL is used to bypass B cell antigen-receptor engagement, the naive T cells enlarge and display activation antigens, but fail to produce lymphokines, proliferate, or promote B cell blastogenesis. Presentation of HEL by tolerant B cells, which are no longer able to signal effectively through their antigen receptors, results in an identical pattern of incomplete T cell activation. Addition of a stimulating anti-CD28 antibody and blocking of CD28 signals with CTLA4/Ig fusion protein both show that complete activation of naive CD4+ T cells depends on the initial induction of B7 and related costimulatory molecules after HEL binding to nontolerant HEL-specific B cells. Thus, in the absence of adequate constimulation from the B cell, naive CD4+ T cells undergo a form of "partial activation" in which they upregulate surface expression of certain T cell activation antigens, but fail to efficiently produce lymphokine and proliferate. This may explain the different conclusions that have been reached regarding the consequences of B cell antigen presentation to T cells, in that the ability of B cells to activate naive CD4+ T cells depends both on their specificity and their activation state.
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W Y
WY
Department of Microbiology and Immunology, Stanford University School of Medicine, California 94305.
Cooke
M P
MP
Goodnow
C C
CC
Davis
M M
MM
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D018106:CD28 Antigens / Q000502:physiology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D017635:Clonal Anergy; D005260:Female; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D015183:Restriction Mapping
D018106:CD28 Antigens