title: Bromelain treatment of human T cells removes CD44, CD45RA, E2/MIC2, CD6, CD7, CD8, and Leu 8/LAM1 surface molecules and markedly enhances CD2-mediated T cell activation.
abstract: Treatment of T cells with the cysteine protease bromelain has been widely used to enhance the binding of human T cells to human E (autologous E rosettes) and has been shown to remove surface T cell CD44 molecules. Ligand binding to CD44 has been shown to markedly augment T cell activation. To study the activation potential of bromelain-treated CD44 T cells, we have compared the proliferation of sham- and bromelain-treated normal human PBMC to mitogenic CD2 mAb. We found that bromelain not only removed T cell CD44, but also removed the CD45RA isoform of CD45 as well as E2/MIC2, CD6, CD7, CD8, and Leu 8/LAM1 molecules. T cell proliferation in response to CD2 mAb was increased 325% in bromelain-treated PBMC compared to sham-treated PBMC (p < 0.005). Reciprocal treatment experiments using purified T cells and monocytes demonstrated that the enhancement of T cell CD2 activation by bromelain occurred only when T cells were treated with bromelain and was accompanied by increased adhesion of T cells to monocytes. These data demonstrate that expression of portions of the extracellular domains of the CD44, CD45RA, E2/MIC2, CD6, CD7, CD8, and Leu 8/LAM1 surface molecules are not required for CD2 activation of human T cells. Rather, the removal of these surface molecules by bromelain is associated with enhanced T cell-monocyte aggregation and enhanced CD2-mediated T cell activation. Taken together with data that CD44, E2/MIC2, CD6, and CD7 mAb inhibit CD2/lymphocyte function-associated Ag-3-mediated cellular interactions and also augment CD2-mediated triggering of T cells, these data suggest that members of the bromelain-sensitive group of surface molecules may comprise a set of CD2-associated adhesion ligands that acts in concert to modulate human T cell activation.
mesh_terms: D000071443:12E7 Antigen; D015703:Antigens, CD / Q000276:immunology* / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D015153:Blotting, Western; D001963:Bromelains / Q000494:pharmacology*; D018801:CD2 Antigens; D002448:Cell Adhesion / Q000276:immunology; D015815:Cell Adhesion Molecules / Q000276:immunology* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D019041:L-Selectin; D008213:Lymphocyte Activation / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology* / Q000378:metabolism; D009000:Monocytes / Q000276:immunology; D011971:Receptors, Immunologic / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors
chemical_list: D000071443:12E7 Antigen; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; C061828:CD99 protein, human; D015815:Cell Adhesion Molecules; D008562:Membrane Glycoproteins; D011971:Receptors, Immunologic; D019041:L-Selectin; D001963:Bromelains