Rapid signaling to B cells by antigen-specific T cells requires CD18/CD54 interaction.
This study reports early B and T cell signaling events during cognate interactions between a human B cell line pulsed with peptide and an Ag-specific T cell clone. As has been previously reported, peptide in the context of the appropriate class II molecule stimulated a rise in intracellular calcium [Ca2+]i in the Ag-specific T cell clone. The activation of the T cell clone was associated with a reciprocal rise in [Ca2+]i in the B cells. Engagement of receptors on the B cell surface by the T cell also was associated with inositol phospholipid turnover comparable to that elicited by stimulation through sIg. Early signaling events in B cells can therefore be stimulated in cognate interactions with Ag-specific T cells, without the direct engagement of Ig receptors. A class II deficient B lymphoblastoid mutant, 6.1.6, which was incapable of presenting peptide to the T cell clone, could be stimulated to produce a rise in [Ca2+]i if the T cell clone was activated by monoclonal antibodies to CD3. Therefore, the interaction of class II molecules on the B cell with the TCR and/or the CD4 accessory molecule was not essential for T-dependent B cell activation. However, T-dependent signalling of B cells was profoundly inhibited by mAb to CD18 (beta-chain of LFA-1) on the T cell or CD54 (ICAM-1) on the B cell, demonstrating the importance of this pair of adhesion molecules in early T-B cell interactions.
Lane
P J
PJ
Department of Microbiology, University of Washington, Seattle 98195.
McConnell
F M
FM
Clark
E A
EA
Mellins
E
E
D015703:Antigens, CD / Q000502:physiology*; D001402:B-Lymphocytes / Q000502:physiology*; D018845:CD11 Antigens; D018821:CD18 Antigens; D002118:Calcium / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000502:physiology*; D002450:Cell Communication; D002478:Cells, Cultured; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1; D013601:T-Lymphocytes / Q000502:physiology*
D015703:Antigens, CD; D018845:CD11 Antigens; D018821:CD18 Antigens; D015815:Cell Adhesion Molecules; D007295:Inositol Phosphates; D018799:Intercellular Adhesion Molecule-1; D002118:Calcium