Cell Surface Immunoglobulin

Abstract

Cells from an established line of Burkitt lymphoma (Daudi) were enzymatically radioiodinated, and labeled Ig from the cell surface was isolated and studied. Subcellular fractionation of labeled cells confirmed that intracellular proteins from the cytoplasm are not iodinated by this method. Radioactive Ig was identified as monomeric (8S) IgM, and an average of 105 Ig molecules was found per cell. Ig molecules could be released from the plasma membrane by detergent lysis under nonreducing conditions indicating that attachment of Ig to the plasma membrane occurs via noncovalent interactions. The ratio of µ/L radioactivity in surface Ig was the same as that of total cellular Ig radioiodinated in solution suggesting that a large portion of the Fc fragment is not buried within the membrane. In contrast to the results obtained with cell surface Ig, most intracellular Ig was found as "free" µ- and L chains regardless of whether lysates were labeled with 125I or cells were labeled with leucine-3H. The results indicate that only a small percentage of the total Ig of Daudi cells is associated with the cell surface and suggest that covalent assembly of Ig occurs at or near the time that the molecule becomes part of the plasma membrane. Similarities between cell surface Ig on normal splenic lymphocytes and Daudi cells suggest that the latter is a neoplasm of bone marrow-derived lymphocytes.

The K-Chains of the Immunoglobulin From a Continuous Culture of Human Lymphocytes (Daudi) Have an Unusual Molecular Size

“…I t has been used to study plasma membraneassociated immunoglobulin (M-Ig) (2,3), complement component receptors (4), f12 microglobulin, I as well as other problems in cell biology (5). We report here that M-Ig of Dandi has a molecular size of about 330,000 daltons.…”

Specific Suppression of the Antibody Response by Antibodies to Receptors

“…0.1 ml of a 1:10 dilution of antiserum to TEPC 15 was added to cultures at the time of immunization or 1, 2, or 3 days later. The same amount of antiserum to MOPC 167 was added to other 15. The following day the animals were immunized intravenously with 109 pneumococci in 0.2 ml of 0.15 M NaCl or with 0.2 ml of a 20% sheep-erythrocyte suspension in 0.15 M NaCl; the spleens were individually assayed for PFC against either untreated or sheep erythrocytes coated with pneumococcal C-polysaccharide at day 4 after immunization. The number of plaques is given per spleen, and it represents the average of four spleens (five slides per spleen).…”

“…The presence of immunoglobulin molecules on the surface of lymphoid cells, particularly on cells derived from bone marrow, is now well established (1)(2)(3)(4). This evidence includes the demonstration of immunoglobulin molecules on the surface of lymphoid cells by immunofluorescent techniques with antisera to immunoglobulins (1), by the adherence of immunocompetent cells to bead columns coated with antisera to immunoglobulins (2), and by isolation of immunoglobulins from the surface of malignant and normal lymphoid cells (3,4).…”

“…This evidence includes the demonstration of immunoglobulin molecules on the surface of lymphoid cells by immunofluorescent techniques with antisera to immunoglobulins (1), by the adherence of immunocompetent cells to bead columns coated with antisera to immunoglobulins (2), and by isolation of immunoglobulins from the surface of malignant and normal lymphoid cells (3,4). Thus far, nonspecific suppression of the antibody response has been achieved by antisera directed against the heavy or light chains of immunoglobulins (5,6).…”

PRODUCTION OF a RUNTING SYNDROME AND SELECTIVE ΓA DEFICIENCY IN MICE BY THE ADMINISTRATION OF ANTI-HEAVY CHAIN ANTISERA

“…By hypothesis, the specific combination of antigen with its receptor(s) results in activation of immune differentiation and subsequent synthesis of antibody, although under certain conditions specific inactivation and tolerance can ensue (1,2). Antigen receptors located on the surface of certain lymphoid cells (3)(4)(5)(6)(7)(8)(9) are considered to be representative of the eventual cell product with regard to both specificity and immunoglobulin class (10)(11)(12)(13). Therefore, the use of antibody directed against a particular class of heavy chain determinants displayed by antigen receptors could conceivably lead to the selective inhibition of the production of that immunoglobulin class resulting in an experimental dysgammaglobulinemia.…”