Influence of specificity of reagents and of behaviour of cell surface Ig on the detection and enumeration of immunoglobulin-bearing lymphocytes in humans.

Some parameters likely to influence detection and classification of human B-lymphocytes using anti-immunoglobulin (Ig) sera have been investigated. Of 20 separate mono- and polyspecific native or conjugated anti-Ig sera analysed by a passive haemagglutination technique, 13 exhibited non-specific reactivity. This technique showed no consistent correlation between the titre of individual sera against Fab2 and whole IgG respectively. The indirect immunofluorescence (IF) method applied to detect surface Ig on blood lymphocytes seemed to detect Fc-bearing rather than Ig-bearing cells. The direct method generally yielded fewer reacting cells (5%) than the indirect (10-25%), suggesting that Fc-bearing cells are more numerous than Ig-bearing cells. The Ig-bearing blood lymphocytes seemed to belong preferentially to the IgM class. Passively adsorbed Ig did not appear to contribute significantly to the number of Ig-bearing cells detected. Anti-Ig sera induced redistribution and some endocytosis of surface Ig but this did not markedly affect detection of Ig-bearing cells.