Cultured lymphoid cell lines from normal subjects: membrane associated immunoglobulins studied by the mixed antiglobulin reaction

Detection of circulating immune complexes with a modified Raji cell technique

A modification of the Raji cell technique for the detection of circulating immune complexes is described. Raji lymphoid cells bind immune complexes via the C 3 receptor. Prior to incubation with the test serum it is necessary to block the IgG Fc receptor which would interfere with the assay. In the present modification the IgG Fc receptor is blocked with monoclonal IgG myeloma proteins thereby facilitating the detection of C 3 bound immune complexes with fluoresecein-conjugated anti-light chain serum. This modification is presently used in a survey of immune complexes in a number of autoimmune diseases.

Increased tetraploidy: cell-specific for the Gardner gene in the cultured cell

Human hereditary tumors in vivo are known to show tissue specificity. Increased endoreduplication with tetraploidy has been shown to occur in cultures established only from tissue containing epithelium (skin and colonic polyps) from patients with the Gardner syndrome. Cultures established from blood (short-term lymphocyte and lymphoid suspension) and connective tissue (subcutaneous tissue, lipoma, mesentery, and sebaceous cyst) from the same patients did not show increased tetraploidy. These observations demonstrated that tetraploidy as an expression of the gene for the Gardner syndrome was cell-specific in vitro and added further evidence that increased tetraploidy could be used for detection of the Gardner gene in families at risk.

Specificity of human lymphocyte complement receptors

Erythrocytes, bone marrow-derived lymphocytes, monocytes, and granulocytes were shown to have a receptor activity for C4. Theis C4 receptor activity was studied in relation to the previously identified C3b and C3d receptors. By assay for inhibition of rosette formation by fluid-phase complement (C), only two different lymphocyte C receptors were demonstrated. The immune adherence receptor, the only one of the two shared in common with erythrocytes, was specific for C4 or the C3c region of C3b, but was unreactive with C3d. The other lymphocyte receptor, the C3d receptor, was specific for C3d fragments, but would also react to a lesser extent with the C3d region of uncleaved C3b. ThC3d receptor did not react with either C3c or C4. This specificity of the C3d receptor allowed certain cells which contained only C3d receptors to form rosettes with EAC1-3b and EAC1-3d, but not with EAC14. However, because C3d receptors bound EAC1-3d or C3d fragments more firmly than they did EAC1-3b or C3b fragments, many other types of cells containing only C3d receptors, formed rosettes with EAC1-3d but not with EAC1-3b. Erythrocytes and those lymphocytes which contained only immune adherence receptors, formed rosettes with EAC14 and EAC1-3D but not with EAC1-3d. A double-label assay was devised for the simultaneous detection of both types of C receptors on individual lymphocytes. This assay involved fluorescence labeling of one of the two C receptors with soluble C fragments in combination with the usual rosette method for labeling the other type of C receptor. With this double-label assay, it was observed that the two different lymphocyte C receptors capped independently and thus were located on different molecules which could each move through the fluid membrane matrix independently of the other.

Two different complement receptors on human lymphocytes. One specific for C3b and one specific for C3b inactivator-cleaved C3b

IN THE PRESENT STUDY IT WAS SHOWN THAT NORMAL PERIPHERAL LYMPHOCYTES HAVE TWO DIFFERENT COMPLEMENT RECEPTORS: one for C3b (the immune adherence receptor) and one for C3b subsequent to its cleavage by C3b inactivator. The two receptors are not cross-reactive and were shown by tests with various antisera to be antigenically distinct. Both the immune adherence receptor and the receptor for C3b inactivator-cleaved C3b were found on normal peripheral lymphocytes and on cultured lymphoblastoid cells. In 15 out of 18 chronic lymphatic leukemia patients, the immune adherence receptor was either partially or completely missing from the peripheral lymphocytes, while the lymphocyte receptor for C3b inactivator-cleaved C3b was retained. Normal erythrocytes, on the other hand, were found to have only the immune adherence receptor. Granulocytes from normal peripheral blood appeared to have only a receptor for C3b and did not have a receptor for C3b inactivator-cleaved C3b.

The relationship between 2 -microglobulin and immunoglobulin in cultured human lymphoid cell lines

beta(2)-microglobulin was detected on the cell surface and in the medium of human lymphoid cells established in long-term culture. The secretion of beta(2)-microglobulin was relatively uniform when different cell lines were compared, whereas IgG production varied widely. kappa- and micro-membrane antigens were modulated by specific antibody; beta(2)-microglobulin was not modulated. Anti-kappa and anti-micro antisera had no effect on the expression of membrane beta(2)-microglobulin, nor had anti-beta(2)-microglobulin antiserum any effect on the expression of kappa- and micro-membrane antigens.