The effect of heating on the expression and function of CD-2 molecules on human T-lymphocytes.

CD-2 molecules on the surface of human T-lymphocytes endow these cells with the capacity of binding sheep (SRBC) and human red blood cells (HRBC). It has recently become clear that they play an important role in the regulation of T-cell functions. The aim of the present study was to analyze the effect of heating at 45 degrees C for 1 hour on the capacity of human T-lymphocytes to bind SRBC and HRBC and to stain with CD-2 monoclonal antibody. Heating of human peripheral blood lymphocytes (PBL), thymus cells, or cells of the HD-MAR T-cell line drastically reduced their capacity of forming rosettes with SRBC. Heating of human thymus and HD-MAR cells also abrogated the formation of rosettes with HRBC. In contrast, the proportion of cells stained by high concentrations of CD-2 MoAb was reduced by only about 10-15%. Using radioiodine-labeled CD-2 MoAb, heating was found to reduce the number of cell surface E-receptors by 42% on PBL and by 27% on HD-MAR cells. The molecular weight of CD-2 molecules present on heated T-cells was identical with that of E-receptors on unheated cells. Heating was found to abolish antibody-induced capping of CD-2 molecules. Thus, heat treatment of human T-cells resulted in a moderate reduction in the number of cell-surface CD-2 molecules and in impaired mobility of CD-2 molecules in the membrane. It remains possible that in addition heating may affect the functional integrity of E-receptors or induce metabolic alterations detrimental for rosette formation.