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Notes: A minor population of T cells expresses a heterodimeric antigen receptor composed of y and A chains (TcR-1). In blood from adults, two subsets of Tγδ cells can be identified by the monoclonalantibodies (MoAb) BB3 and A13. Little is known about the distribution and markers of these subsets early in life. We have therefore examined both the frequencies of these cells in cord blood and their expression of the cytotoxicity-associated marker serine esterase (SK). using immunocytochemical techniques.Our data show lower percentages of TcR-1+ cells in the blood of newborns compared with that in adults. However, the ratio of the Al3+/BB3 cells was significantly higher in cord than in adult blood. Whereas virtually all the adult TcR-1+ cells in blood were SE-positive. only a small proportion of the cord blood cells earned ibis enzymes. This was; restricted lo the BB3+ Tγδ -cell subset in the cord.Our data suggest different characteristics of the TcR-1+ cells in blood from newborns compared with adult blood, and study of the functions of the different subsets, e.g. cytotoxicity. will be important in understanding their particular role in immunity.

Notes: Epithelial expression of class II antigens encoded by the major histocompaatility complex (MHC) has been proposed as a means by which autoimmune thyroid disease may be initiated and maintained. We studied a rat thyroid epithelial cell line (FRTL-5), which constitutively expresses class I (OX18) but not class II (OX6orOX17)determinants to quantify in vitro MHC antigen induction using flow cytometry. Recombinant rat γ interferon (rlFN-γ) induced dosedependent expression of OX6(l-A) antigen at 〉48 h (maximum 80–90% of cells in culture at 100 U/ml). whieh was abrogated by DB-I, a munoclonal antibody to rat IFN-γ OXI7 antigen (I-E) was also induced (86%) and OX18 (class I) markedly increased under these conditions Other thyroid-active agents including the calcium ionophore A23187. dibutyryl cyclic AMP. thyroid-stimulating autoantibodies from Graves’ disease patients (LATS), and TSH. caused no I-A induction. Supernatants from spleen cells stimulaled with plant lectins(concanvialin A or phytohaemagglutinin). but not lectin alone. evoked substantial class II induction. which was inhibited yy DB-1. These findings suggest that IFN-γ is the central mediator of thyroid epithelial class II expression, FRTL'S provides a powerful model for the analysis of thyroid MHC elass 11 dynamies and a potential means of analysing the role of epithelial class II in autoimmune pathogenesis.

Notes: The CD5 molecule is expressed by most T cells but it is present on a minor B cell subset. Whilst several studies have provided information on the physiological role of T cell CD5, the functional role of CD5 on B lymphocytes remains unclear. To address this question, tonsillar CD5+ B cells were sorted by dual-colour fluorescence and FACS. Sorted cells were stimulated with polyclonal anti-IgM antibodies (Ab), and monoclonal (MoAb) F(ab')2 fragments of anti-CD5. Proliferative responses were evaluated by enumeration of Ki-67 positive cells using quantitative flow cytometry. Co-stimulation with anti-CD5 MoAb for 3 days did not affect the anti-IgM and IL2-induced proliferation of CD5+ B cells. This was seen under conditions where the anti-CD5 was soluble, adsorbed to the microwells or cross-linked by anti-mouse antibodies. Fewer CD25+ cells were detected, however, in the presence of anti-CD5. In contrast, the proliferative response of CD5+ B cells prestimulated for 3 days with IL-2 and anti-IgM, was sustained in a further 3-day culture period when anti-CD5 was added. It is concluded that CD5 occupancy might provide an additional signal to activated CD5+ B cells favouring their proliferation and differentiation into autoantibody secreting cells.

Notes: The authors used murine pregnancy as a model to investigate the regulation of IgG glycosylation. Pregnancy is associated with decreased levels of circulating IgG. The oligosaccharides on this IgG from late (day 15), but not early (day 8), pregnant Balb/c mice exhibited increased levels of terminal galactose. The levels remained elevated 8 days post-partum in lactating mice. Nonetheless, splenic β1,4-GalTase mRNA and enzyme activity remained relatively constant throughout pregnancy and into lactation. This was in contrast to a pregnancy-associated increase in mammary gland β1,4-GalTase mRNA. Thus the increased IgG galactose levels seen in pregnancy are regulated by mechanisms which are independent of transcriptional control of β1,4-GalTase expression.

Notes: CD5 is associated with the B-cell antigen receptor (BcR) complex. As an approach to understanding its role in B-cell function, the authors investigated the capping and modulation of CD5 and surface IgM (sIgM). Tonsillar B cells were treated withanti-IgM or anti-CD5 antibodies, capping examined after 1 h (by fluorescence microscopy) and modulation after 24 h (by flow cytometry). CD5 co-capped and co-modulated with sIgM. Of various drugs tested, only the protein tyrosine kinaseinhibitor (genistein) had any effect on capping and co-capping. Capping of sIgM (and co-capping of CD5) but not capping of CD5 (or co-capping of sIgM) was inhibited by genistein. None of the other drugs affecting PKC or cytoskeletal structures (colchicine and cytochalasin D) had any effect. However, the PKC inhibitors, staurosporine and H-7, inhibited the modulation of sIgM by anti-IgM but not CD5 by anti-CD5. In contrast, PKC activators, PMA and mezerein, inhibited modulation of CD5 by anti-CD5 but notsIgM by anti-IgM. This suggests that direct ligation of CD5 utilizes different signalling pathways compared with sIgM. It seems likely that in CD5+ B cells, interaction of CD5 with its ligand CD72 modulates signals transmitted through theBcR.

Notes: Our early concepts of the normal role of B cells in immunity focused on their ability to produce antibodies (Ab) and in the case of autoimmune diseases autoAbs, some of which were pathogenic. Over the past 10 years, it has became apparent that B cells display a variety of characteristics, other than Ab production, which could contribute to autoimmunity. They normally play a role in the development of lymphoid architecture, regulating T-cell subsets and dendritic cell (DC) function through cytokine production, and in activation of T cells. Receptors editing is also important in B cells which aids in immunity to infection and, possibly, prevention of autoimmunity. Transgenic animal models have now shown that B cells are necessary for many autoimmune diseases although their Ab products are not required in some cases. Negative signalling by CD5 and other molecules, such as CD22, in maintaining tolerance through recruitment of src-homology two domain-containing protein tyrosine phosphatase-1 has also been documented. In fact, we have now reached a new era whereby the B cell has returned as an important contributor to autoimmune disorders, so that the race is on to characterize signalling regulation via the B-cell receptor and coreceptors. Identification of such molecules and their potential defects should lead to effective ways of controlling the immune response and in particular preventing the development of autoimmune states. The classical view of B cells in the biology of immune responses to infectious and self-antigens (Ag) that they promote immunity primarily by producing Ab turns out to be rather naïve. Indeed, studies over the last few years indicate that this view is far from complete, and suggest that B lymphocytes have extraordinarily diverse functions within the immune system. Furthermore, it is becoming increasingly clear that the pathogenesis of autoimmune diseases cannot solely be accounted for by T cells, and intrinsic abnormalities of B cells have been described in such conditions. In this brief review we highlight some recent observations in the context of B lymphocyte in pathophysiology, and focus on their revival as pivotal players the pathophysiology in autoimmune diseases. Yet, it remains difficult to provide a model of how important B cells are in immunity and autoimmunity.

Notes: Plasma cells synthesizing rheumatoid factors (RF) were identified by fluorescent staining of sections of synovium and macrophage-depleted cells from dispersed synovial tissue. The latter avoided problems related to sampling errors in studying tissue sections and in the uncertainty raised by the staining of macrophages with intracellutar complexes. Plasma cells producing IgG predominated, and seropositive patients had a higher proportion of IgM producers than seronegative subjects. None the less, in both groups of patients more than 90% of the IgM plasma cells were synthesizing RF. whereas the corresponding figure for IgG was between 50% and 60% Only around 10% of IgA plasma cells were positive for RF. The high percentage of IgM plasma cells making RF would lend to argue for an IgG-specific response and against direct polyclonal activation as the stimulus. The percentage of IgG-producing cells positive for RF is also consistent with a dominant response to IgG. Accepting the difference in the relative proportion of total IgM- to IgG-producing plasma cells in seropositive as against seronegative patients, the close similarity between the two groups in the fraction of cells making RF favours Ihe view that the two groups have a comparable underlying immunopathology dependent on IgG autosensitization. From the technical standpoint, the dispersed cell method gives results in line with those obtained with sections but which are easier to read, whereas the fluorescent techniques described give clear and reproducible results for the detection of RF of different heavy-chain isotype.

Notes: In a recent study we have observed a high frequency expression of cross-reactive idiotypes encoded by genes from the relatively small VH4 family of immunoglobulin heavy chain genes in cord blood B-lymphocyte lines. Furthermore, we have demonstrated a selective pattern of expression of two VH4-associated cross-reactive idiotype (CRI) in B-lytnphocyte lines established from CD5+ and CD5- cord blood B-lymphocytes. There was a restricted expression of one CRI marker recognized by the 9G4 monoclonal antibody in lines established from CD5+ B-lymphocytes but not in those established from the CD5- population. In the current study we examine the molecular basis for the selective pattern of CRI expression. Nucleotide-sequence analysis of functional immunoglobulin heavy chain (IgH) gene rearrangements in three CD5 + lines expressing the CRI recognised by 9G4 reveal that all use a single gene from the Vh4 family, the V4.21 gene. However, all three lines have distinct third complementarity determining regions (CDR3) implying different clonal origins. In contrast, four cord blood cell lines (two established from CD5+ B-lymphocytes) expressing the CRI recognized by MoAb Lcl have functional IgH gene rearrangements involving two ditferent genes from the Vh4 family, the V71–4, and V2–1 genes. Antigen specificity analysis reveals that all three 9G4-reactive lines produce antibodies that react with the I and/or i red blood cell carbohydrate antigens. These data suggest that the distinction in VH4 gene use in CD5+ B-lymphocytes in cord blood results from a selection process in vivo that shapes the repertoire of CD5+ B-lymphocytes. This study extends recent observations that the monoclonal anti-CRI antibodies 9G4and Lc1 are markers of two distinct subgroups of proteins encoded by two subsets of genes within the VH4 family. Furthermore, it appears that amino acid residues in framework region one and complementarity determining region two are critical for the expression of the cross reactive idiotypes and the serological distinction between the two subgroups of proteins.