Neuraminidase- and trypsin-induced exposure to membrane receptors for IgG and IgM molecules on human peripheral blood lymphocytes.

Brief incubation of human peripheral blood lymphocytes with vibrio cholerae neuraminidase (VCN) or trypsin revealed hidden membrane receptors for IgG and IgM molecules. The hidden receptors were found on T lymphocytes as shown by double-label and mixed rosetting experiments and by studies of T-enriched populations. Although IgM receptors were undetectable on freshly isolated lymphocytes, a mean of 17.1% of VCN-treated lymphocytes rosetted with ox erythrocytes coated with IgM antibody (EA-IgM). Prior to trypsin treatment a mean of 14.6% of human T lymphocytes rosetted with ox red cells coated with IgG antibody (EA-IgG). After incubation with trypsin this figure increased significantly (P less than 0.005) to 44.5%. VCN-treatment also significantly increased (P less than 0.005) the mean percentage of EA-IgG rosette-forming T cells to 38.5%. The T-cell receptor for IgG was shown to be trypsin-resistant while the IgM receptor was shown to be trypsin-sensitive. Using mixed rosettes, a tentative T-cell subset was identified which expressed both IgG and IgM membrane receptors. Also, a minor subset with IgM receptors alone and a larger subset with only IgG receptors were identified.