Independent Movement of IgD and IgM Molecules on the Surface of Individual Lymphocytes

Abstract It is now generally accepted that immunoglobulins (Ig) on the membrane of lymphocytes are mobile in the plane of the membrane itself. The reaction of divalent antibodies with the Ig molecules, which were originally diffusely distributed, induces cross-linkage and aggregation of the Ig molecules. These aggregates are then actively transported to one pole of the cell where they form the so-called caps. This capping process is markedly inhibited in the cold and can be blocked by different drugs (1, 2). We used this phenomenon for the investigation of Ig molecules of two different classes (IgM and IgD) on individual lymphocytes. Materials and Methods. Cord blood lymphocytes from 20 healthy babies and peripheral lymphocytes from 20 adults were investigated for the presence of membrane-bound Ig in immunofluorescence. Lymphocytes were obtained by gradient centrifugation with the Isopaque Ficoll technique (3). Cells were tested for viability and stained in suspension. The direct immunofluorescence technique with fluorescein-isothiocyanate (FITC)3 and tetramethyl-rhodamine isothiocyanate (TRITC) conjugated antisera (4) was performed by incubating 1 to 3 × 106 viable lymphocytes suspended in 0.05 ml phosphatebuffered saline (PBS) with 0.05 ml of the conjugate at either 0°C, 4°C or 37°C for 30 min. The cells were washed twice with PBS.