title: Monocytes are required to trigger Ca2+ uptake in the proliferative response of human t lymphocytes to staphylococcus aureus protein A.
abstract: We have used the T-cell mitogen Staphylococcus aureus protein A (SpA) to study the role of monocytes in the early events of T-lymphocyte activation. The mitogenic response of human peripheral blood mononuclear cells (PBM) was compared to the response of populations enriched for T cells by E-rosetting (PBM-E+). In response to SpA, the [3H]thymidine uptake of PBM-E+ was reduced by 80% compared to PBM. The reduced response of PBM-E+ was completely restored by the addition of irradiated PBM-E- or the monocyte-like human cell line U-937 but not by addition of irradiated PBM-E+. A direct interaction of SpA with monocytes is important since proliferative responses could be generated by preincubation of U-937 with SpA followed by washing and subsequent addition to PBM-E+; incubation of PBM-E+ with SpA followed by washing and subsequent addition of U-937 did not result in a proliferative response. To further delineate the role of the monocyte, we examined the ability of soluble SpA, U-937, or U-937 preincubated with SpA to trigger Ca2+ flux into T lymphocytes, an early step in initiation of the proliferative response. SpA-pretreated U-937, but neither SpA nor monocytes alone, triggered Ca2+ movement into the T lymphocytes. This defines a new role for the monocyte in the early events of T-lymphocyte activation.
mesh_terms: D002118:Calcium / Q000378:metabolism*; D006801:Humans; D008213:Lymphocyte Activation; D009000:Monocytes / Q000502:physiology* / Q000528:radiation effects; D010835:Phytohemagglutinins / Q000494:pharmacology; D012397:Rosette Formation; D013205:Staphylococcal Protein A / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
chemical_list: D010835:Phytohemagglutinins; D013205:Staphylococcal Protein A; D002118:Calcium