Immunoglobulin Structure, Synthesis, Secretion, and Relation to Neoplasms of B Cells

Mechanism of effector cell blockade--IV. Induction by monoclonal anti-mu or anti-idiotypic antibody, role of secreted IgM and mechanism of decreased secretion

Effector cell blockade (ECB), the inhibition of antibody synthesis by antigen or antigen-antibody complexes, was shown to be induced by monoclonal anti-mu or anti-idiotypic antibodies. An initial event in the induction of blockade was demonstrated to be the build up on the cell surface of a complex of membrane Ig, and either antigen or anti-mu or anti-Id antibody, together with secreted IgM. Trapping of secreted IgM in this complex was not, however, sufficient to account for the overall reduction in antibody secretion. This reduction was not due to reduced translation of mu mRNA, but rather to blockade of the normal process of assembly of the IgM molecule which was followed by increased intracellular degradation of intermediate precursor molecules. These findings have shown ECB to be a rapidly induced negative feedback control of IgM secretion which, at least initially, could be reversed. ECB may act in vivo as a flexible first-line mechanism for prevention of overproduction of IgM antibodies.

Signet-ring cell lymphoma. Ultrastructural and immunohistochemical features of three varieties

An ultrastructural and immunohistochemical study was performed on three malignant lymphomas of follicular center cell origin with signet-ring cells. The first case corresponded to a diffuse lymphoma with follicular center cells and plasmacytic features; the other two cases corresponded to the nodular centrocytic-centroblastic category. The neoplastic lymphocytes contained Russell bodylike inclusions, clear vacuoles, and ill-defined eosinophilic masses, respectively, which produced a displacement of the nuclei to the periphery. Ultrastructurally, there were three different morphologic types because of the following cytoplasmic changes: the accumulation of electron-dense granular material in the cisternae of the rough endoplasmic reticulum; the formation of clear vacuoles with a smooth limiting membrane; and, the presence of granular-fibrillar and crystalline material in the hyaloplasm without a limiting membrane. The first type of signet-ring cell contained monoclonal immunoglobulin (IgM-K). No immunoglobulins were found in the clear cytoplasmic vacuoles of the second type; however, the rim of cytoplasm stained for IgG, kappa and lambda. Finally, the third type showed IgG and kappa light chain in the hyaloplasmic inclusions. It is concluded that the signet-ring cell appearance is due to an abnormal production and secretion of immunoglobulins.

Chronic lymphocytic leukaemia and IgG heavy chain disease

A 64-year-old woman who has suffered from chronic lymphocytic leukaemia since 1976 is discussed. In 1978, an abnormal protein component was found in her serum by means of immunoelectrophoresis. Using the techniques of immunoselection of the serum immunoglobulins and immunofluorescence of the bone marrow cells, it was demonstrated that this component consists of IgG1 heavy chains only. The native protein, COL, consisted of a dimer linked by disulphide bonds of a molecular weight of 80 000 daltons. Its monomeric unit had a molecular weight of 40 000 daltons, as determined by SDS-polyacrylamide gel electrophoresis after reduction with 2-mercaptoethanol. Protein COL was not produced by the leukaemic cells (which bore IgM-lambda on their membrane) but by a morphologically distinct clone of lymphoid cells. After therapy with chlorambucil, the level of the heavy chain disease protein in the serum decreased substantially.