Identification Of CD4 Research Articles

Identification of CD4 and major histocompatibility complex functional peptide sites and their homology with oligopeptides from human immunodeficiency virus type 1 glycoprotein gp120: role in AIDS pathogenesis.

CD4 molecules interact with class II major histocompatibility complex molecules as a critical costimulatory signal in CD4+ cell immune activation. CD4 also recognizes a specific region of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 forming a binding site for early stages of HIV-1 infection. We designed two software packages, AUTOMAT and CRITIC, which allowed us to identify similarities between regions of HIV-1 proteins and immunoregulatory protein sequences stored in data banks. In this report we have characterized (i) a pentapeptide, SLWDQ, found in both CD4 and HIV-1 gp120, which surprisingly had remained undetected in these two well-studied molecules until now, and (ii) an HLA sequence corresponding to the putative functional site of H2 I-A. We found that a region of gp120 (residues 254-263) known to be similar to a sequence in HLA class II beta chain overlaps this functional region. We showed experimentally that these two CD4 and HLA peptide segments inhibit CD4+ cell immune activation. There is strong inhibition (50% up to 80%) of immune activation by SLWDQ-containing gp120 segments and a lesser inhibition by the gp120 HLA-homologous segment. In addition, we found that SLWDQ induced in HIV-1-infected individuals a humoral (antibody) and cellular (cytotoxic T lymphocyte) immune reaction. We propose that these HIV-1 gp120 segments, together with the known CD4-binding region, may contribute to the HIV-1-induced immunosuppression by two mechanisms affecting CD4-HLA interaction during T-cell immune activation: autoimmune reaction toward CD4 and direct interference with the CD4-HLA costimulatory signal inducing CD4+ cell anergy with, as a consequence, generation of immunosuppression.

Interleukin-6 induction in vitro in mouse brain endothelial cells and astrocytes by exposure to mouse hepatitis virus (MHV-4, JHM)

Interleukin-6 (IL-6) induction, as detected by bioassay and Northern analysis, was examined in vitro in endothelial cells or astrocytes derived from BALB/c (susceptible) or SJL (resistant) mice following exposure to mouse hepatitis virus (MHV-4) or UV inactivated MHV-4 (UV-MHV-4). In BALB/c endothelial cells, up to 16-fold more IL-6 (> 640 U/ml) was induced, compared to SJL cells which showed a minimal response (40 U/ml), relative to basal levels (< 20 U/ml). In contrast, both BALB/c and SJL astrocytes showed a substantial IL-6 response to MHV-4 and UV-MHV-4 exposure, although a strain difference persisted. Despite strain and cell specific differences in released IL-6, equivalent levels of IL-6 mRNA were induced in all cell types following exposure to MHV-4 or UV-MHV-4.

Fibroblast stimulation in schistosomiasis. XII. Identification of CD4+ lymphocytes within schistosomal egg granulomas as a source of an apparently novel fibroblast growth factor (FsF-1).

Granulomas that form around Schistosoma mansoni eggs deposited in the liver secrete a variety of fibrogenic factors that may provide a molecular link between chronic inflammation and hepatic fibrogenesis in schistosomiasis. We recently isolated from conditioned medium of egg granuloma cultures a approximately equal to 60-kDa heparin-binding growth factor for fibroblasts. Because this protein is distinct from other defined heparin-binding growth factors, we designated it "fibroblast stimulating factor-1" (FsF-1). We now report that FsF-1 is a lymphokine. We prepared IgG antibody against purified FsF-1 and determined that it did not cross-react with a variety of growth factors or recombinant interleukins. Using two-color flow cytometry of dissociated granuloma cell suspensions, we observed that approximately 20% to 25% of granuloma CD4+ lymphocytes express surface FsF-1. We isolated CD4+ granuloma lymphocytes by FACS and observed that these cells spontaneously secrete into culture supernatant a fibroblast mitogen that is neutralized by anti-FsF-1 antibody. Furthermore, anti-FsF-1 can specifically immunoprecipitate a metabolically labeled protein produced by the granuloma CD4+ lymphocytes. The labeled protein has the same apparent molecular mass (approximately equal to 60 kDa) as FsF-1 purified from granuloma culture supernatants. These findings define CD4+ lymphocytes as a source of FsF-1. Because FsF-1 has biologic and chemical features distinct from most other defined lymphokines and from other heparin-binding growth factors, FsF-1 appears to be a novel lymphokine.

Sequential Immunohistologic Analysis of the Skin Following Allogeneic Bone Marrow Transplantation

Graft-vs-host disease is generally viewed as an immunologically mediated disease. In search of additional tools for early diagnosis and an elucidation of the pathogenic mechanisms we investigated the expression kinetics of hemopoietic differentiation and class II alloantigens on both resident and passenger skin cells after bone marrow transplantation. HLA-DR antigens, which are found normally on the dendritic epidermal Langerhans cells only, are synthesized and expressed by keratinocytes within lesions of acute and chronic cutaneous graft-vs-host disease. Within non-lesional skin, however, during the course of cutaneous graft-vs-host eruptions, no clear cut expression of keratinocyte-bound HLA-DR antigens can be identified, suggesting that this phenomenon is locally restricted rather than generalized. Furthermore, our data indicate that within lesions clinically suggestive of cutaneous graft-vs-host disease but lacking diagnostic histopathologic criteria, KC-bound HLA-DR antigens can be readily identified. The second class II alloantigens investigated within the epidermis, the HLA-DQ antigens, were seen on Langerhans cells only and were not or only rarely detectable on keratinocytes. Several subtypes of CD3+ T lymphocytes were present in the epidermis of acute graft-versus-host lesions: one portion of CD3+ T lymphocytes also displayed the CD8 antigen; one portion, mainly localized within the basal layer, displayed the CD8 and/or the CD4 antigen; and one portion did not allow identification of CD8, CD4, or Leu7 antigens. In chronic cutaneous graft-versus-host lesions CD3+/CD8+ T lymphocytes predominated. CD1+ epidermal Langerhans cells were reduced in number and appeared rounded with blunt dendrites both in acute and chronic cutaneous graft-vs-host disease, but also, though to a lesser extent, within normal appearing skin from bone marrow transplanted patients without cutaneous graft-vs-host disease.

Identification of CD4+, 2H4+ (T8 gamma +) suppressor-inducer cells in normal human epidermis and superficial dermis.

Immunohistological staining of frozen sections of normal human skin demonstrated the presence of significant numbers of mononuclear cells expressing novel epitopes associated with CD4-positive suppressor-inducer functions. The cells were located around superficial vessels and within the basal layers of the epidermis and hair follicles. The antigen identified by the various antibodies has been shown to be functionally important in the induction of various suppressor cells capable of abrogating B cell responses to pokeweed mitogen. The presence in the skin of cells with possible down-regulatory functions in the immune response may be significant with respect to surveillance against neoplasms and control of appropriate responses to infectious agents.

A serine protease-encoding gene that marks activated cytotoxic T cells in vivo and in vitro.

Activated cytotoxic T lymphocytes (CTLs) are presumed to be the effectors in the lysis of virally infected or transformed host cells, the mediators of graft rejection, and the potential culprits in a number of autoimmune diseases. Unfortunately, there is no marker available that specifically identifies these cells in vivo, making it difficult to prove unequivocally that CTLs are the effector cells in these immune functions. Mature T cells are usually divided into subsets on the basis of their surface phenotype: Those that express the CD8 antigen are assumed to be potential cytotoxic cells, and those that express the CD4 antigen, potential helper cells. However, the identification of CD4+CD8- CTLs (Golding et al. 1985) and CD4-CD8+ helper cells (Swain and Panfili 1979) both in vitro and in graft rejection in vivo (Rosenberg et al. 1987) limits the usefulness of this division. A more serious problem with using phenotype to imply function is that these markers are expressed on both active and resting T cells. Thus, they cannot be used to distinguish between the cells participating in a localized immune response and those nonspecifically present at the site. To identify cytotoxic lymphocytes more accurately, we used a molecular genetic approach to isolate genes expressed by these cells.