Secretory component: interactions with intracellular and surface immunoglobulins of human lymphoid cells

Unstimulated and PWM-stimulated lymphocytes from normal human peripheral blood, cord blood, peripheral blood of patients with panhypogammaglobulinemia and selective IgA deficiency, as well as human lymphoblastoid cell lines were examined for their ability to bind secretory component (SC) on the surface and in the cytoplasm. SC binding was not detected on the cell surface at any stage of differentiation in these cells. However, binding of SC was detected in the cytoplasm of 2.3% of normal peripheral blood lymphocytes cultured in the presence of PWM for 6 to 7 days, and in two IgA producing lymphoblastoid cell lines. The capability of lymphoid cells to bind SC was not concurrent with J chain production. Although IgA was detected in the cytoplasm of PWM-stimulated lymphocytes from IgA-deficient patients, these cells did not bind SC. The failure to detect surface receptors indicates that SC is not a probable factor determining the homing of IgA precursor cells into exocrine tissues.