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Endogenous and surface labelling techniques were used on human lymphoid cells to characterize intracytoplasmic, membrane and secreted IgD. IgD synthesized by lymphocytes and inserted into the cell membrane displayed a single molecular form with the same mobility in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) as the previously described slow migrating serum IgD1. Plasma cells produced and secreted IgD1 and another IgD corresponding to the faster-moving serum IgD2. Conversion of one molecular form into the other was never observed, thus indicating that neither molecule is a precursor or a degradation product of the other. [ABSTRACT FROM AUTHOR]

Human IgD present in the serum of normal individuals or of patients with Hodakin's disease (having high IgD concentrations) was characterized and compared with five IgD myeloma proteins. IgD was isolated using a highly specific anti-δ insoluble immunoabsorbent from which the bound material was critical with sodium dodecyl sulphate (SDS) or urea. The latter reagent could be removed by extensive dialysis, thus making possible the renaturation of the eluted molecules. The purity ot the IgD thus isolated was confirmed by antigenic analysis. Both k and z light chain determinants were present on serum IgD. although z light chain was predominant with a ratio over the K chain of 2:1, SDS-polyacrylamide slah gel electrophoresis analysis revealed two different molecular forms of serum IgD, one (IgDI) migrating identically to monoclonal IgD, the other (lgD2) having a faster mobility. The difference between the two molecules was entirely, due to the different sizes of their constituent δ chains. Peptide mapping of the two chains (δ,1 and δ2 respectively) and of the δ chain of an IgD myeloma protein was carried out using labelled material. The three molecules displayed a high degree of homolog the δ2 chain differing by the presence of three characteristic extra peptides. The significance of these extra peptides is discussed in the light of the peptide mapping technique employed. [ABSTRACT FROM AUTHOR]

Human peripheral blood large granular lymphocytes (LGL)--that is, cells with intracytoplasmic azurophilic (electron-dense) granules, with a positivity for the cytochemical localization of certain acid hydrolases, and with avid surface receptors for the Fc portion of IgG--have been purified on Percoll density gradients. Approximately 30% of these cells expressed receptors for the third complement component (C3R). They were separated into C3R-positive and C3R-negative cells. C3R+ cells had a significantly greater natural killer (NK) activity against K562 target cells than C3R+ cells. This difference was unrelated to the presence in the C3R+ cells of a contaminant cell type incapable of NK activity, since cytochemical and ultrastructural analysis revealed that C3R+ and C3R- fractions contained comparable LGL numbers. Agarose cytotoxicity assays at the single-cell level demonstrated that C3R+ LGL contained a large number of cells that bound to but did not lyse the target. The remaining fully cytotoxic C3R+ LGL had, however, the same killing and recycling properties as the cells from the C3R- fraction. Electron microscopy and cytochemical studies showed that C3R+ cells had fewer electron-dense granules than C3R- cells and stained more faintly for the localization of alpha-naphtyl acetate esterase. In contrast to C3R- cells, C3R+ LGL displayed morphological features suggesting that an active process of granule formation was taking place. Taken together, the data indicate that C3R+ cells represent a discrete subset or a maturational stage of LGL. [ABSTRACT FROM AUTHOR]

Large granular lymphocytes (LGL) are nonadherent cells with cytoplasmic azurophitic granules, avid receptors for the Fc portion of lgG, and a paranuclear localization of alpha-naphthyl acid esterase or acid phosphatase. LGL constitute the bulk of TG cells (cells wish receptors for sheep erythrocytes and for IGC molecules) and null cells (non-T, non-B cells). In the present study we demonstrate that 20-33% of the circulating human LGL express receptors (or the third complement component (C3R). When TG or null cell fractions from normal individuals or non-T cells from a patient with infantile agammaglobulinaemia (which contained almost exclusively LGL) were rosetted with erythrocytes coated with antibody and complement, a variable number of C3R-bearing cells were detected. Such cells were isolated and analysed further; the great majority of them displayed she cytochemical and ultrastructural features of LGL. [ABSTRACT FROM AUTHOR]

Murine gamma/delta T lymphocytes localize to different epithelial tissues and are phenotypically distinct from peripheral gamma/delta T cell-populations in that they show limited TCR diversity, express the CD8 alpha/alpha homodimer and lack the CD8 beta chain. In humans, a compartmentalization of gamma/delta cells sharing similar phenotypic features has been documented to date only in the case of intestinal epithelium. In the present study we show that about half of V delta 1+ (as well as V delta 1-V delta 2-) gamma/delta lymphocytes, which can be selectively expanded from human lung cancers, coexpress the CD8 alpha/alpha homodimer. The accumulation of intraepithelial CD8+ gamma/delta+ lymphocytes might then be a more general phenomenon, possibly as a result of common mechanisms operating at those sites.