Human CD38 and its ligand CD31 define a unique lamina propria T lymphocyte signaling pathway

CD38, a nonlineage-restricted surface glycoprotein, is an ecto-enzyme (ADP ribosyl cyclase/cADPR hydrolase/EC 3.2.2.6) that regulates cytoplasmic Ca2+ and cell-cell interactions. The molecule also delivers trans-membrane signals, despite a structural ineptitude to the scope. To reconcile these issues in a unitarian model, we compared the effects of CD38 signaling in circulating and residential T lymphocytes, the latter represented by those colonizing the intestinal lamina propria. Results are as follows: 1) LP T cells express an enzymatically active form of CD38, characterized by a modified ratio between cyclase and hydrolase functions; 2) LP T cells do not mobilize Ca2+ upon CD38 ligation, as seen in PB T cells (this condition is due to a lack in activation of PLC- g, constantly observed in PB T lymphocytes); 3) The early steps of CD38 signaling involve activation of lck, syk, and LAT; 4) Late events include synthesis and release of IL-2, IL-4, IL-5, IL-10, IFN-g and GM-CSF; 5) The uniqueness of the CD38 pathway in LP T cells is not caused by impaired interactions with the CD31 ligand. The differences observed concern the signaling machinery that CD38 exploits for its own use and not the interplay with its ligand.

[Idiopathic CD4+ T-lymphocyte deficiency: the clinical evolution of a case]

The case of a patient with Salmonella arizonae sepsis, esophageal candidiasis, and a low CD4+ T lymphocyte count is presented. Follow-up continued for over 2 years after the patient was discharged from the hospital, and his clinical course and clinical-immunological examinations are described. After a period of several years during which the patient had recurrent acute infectious episodes, he improved markedly after cholecystectomy and toilette of the gingival inlets for severe parodontopathy. His CD4+ T cell count increased although it remained below normal values. This case points to possible hypothesis that chronic infective foci may further compromise the immune system when a congenital functional or numerical CD4+ T cell deficit is present.

Functional effects of a monoclonal antibody directed against a distinct epitope on 4F2 molecular complex in human peripheral blood mononuclear cell activation

The 4F2 antigenic complex is expressed on most human cell lines in culture, on monocytes and activated lymphocytes, but not on resting T and B lymphocytes. Monoclonal antibody (mAb) CB43 recognizes an epitope of the 4F2 heterodimer either located on the light chain or dependent on the conformation of the molecule. The binding of CB43 mAb to peripheral blood mononuclear cells (PBMC) induced a dose-dependent comitogenic effect in the presence of submitogenic concentrations of anti-CD3 mAb. Significant amounts of interleukin (IL)-1 beta but not IL-2 or interferon-gamma were released in the supernatant. Pretreatment of monocytes with CB43 mAb increased the phytohemagglutinin-induced T lymphocyte proliferation. However, CB43 mAb did not exert agonistic effects on activated T lymphocytes. Depletion of CB43+ cells from PBMC decreased the proliferation and generation of cytotoxic effector cells induced by a mannoprotein (MP) derived from Candida albicans cell wall but not by recombinant IL-2. Furthermore, depletion of CB43+ cells from PBMC preactivated with MP or rIL-2 led to a significant decrease in their cytotoxic activity. CB43 mAb did not inhibit the growth of cell lines nor the proliferation of T cells. Thus CB43 mAb identifies a distinct functional epitope on the 4F2 molecular complex and might be useful in further studying the role of this molecule in cellular activation.

Cell-mediated immune response in human hepatic echinococcosis. Analysis of antigen-induced lymphoproliferation and NK activity

In vitro cellular immune responsiveness was studied in 25 patients undergoing surgery for hepatic hydatid disease and in 22 matched healthy controls. Proliferation of peripheral blood mononuclear cells (PBMC) induced by phytohaemagglutinin (PHA) was not statistically different in the two groups, while proliferation induced by antigenic preparations obtained from the human commensal microorganism Candida albicans was depressed in patients as compared to healthy subjects. Confirming previous data, antigen specific proliferative response to hydatid cyst fluids was greatly enhanced in patients as compared to controls (P less than 0.01). On the other hand, natural killer (NK) activity was significantly reduced (P less than 0.005). Both impairment of NK activity and lymphoproliferation induced by commensal microorganisms suggest that patients following the parasitic infection present a condition of relevant hyporesponsiveness in cell-mediated defence.

Interleukin-2, interleukin-2 receptor and gamma-interferon synthesis by peripheral blood mononuclear cells in chronic hepatitis delta virus infection

The behaviour of the immune system during liver damage caused by chronic hepatitis delta virus (HDV) infection was evaluated by assessing, in 16 patients with HBsAg+ chronic liver disease and HDV superinfection (15 HBeAg-, 1 HBeAg+), phytohaemagglutinin (PHA)-induced interleukin-2 synthesis and interleukin-2 receptor expression, PHA and staphylococcal enterotoxin B (SEB)-induced gamma-interferon synthesis and, in some cases, the presence of hepatitis B virus DNA (HBV-DNA) within peripheral blood mononuclear cells (PBMC). The results were compared to those obtained in 13 patients without HBV replication (i.e., serum HBV-DNA and liver HBcAg-negative), in 15 with HBV replication (i.e., serum HBV-DNA and/or liver HBcAg-positive) with chronic liver disease without HDV superinfection, and in 15 HBsAg-negative healthy control subjects. The lymphokine pattern in HDV infection was comparable to that of healthy subjects and of HBV non-replicating patients without HDV superinfection. Interleukin-2 receptor expression and gamma-interferon synthesis were however significantly decreased in HDV-negative patients with active HBV replication. HBV-DNA was detected in PBMC from 8 of 23 patients, without any correlation with the lymphokine pattern. Our results suggest that in HDV-related chronic liver disease, immune system alterations are unlikely. HDV superinfection does not affect the occurrence of HBV-DNA sequences within the leukocytes. HBV-DNA in PBMC does not interfere with the interleukin-2 system nor with the gamma-interferon response in HBV- and HDV-related chronic liver disease.

Cell-mediated cytotoxicity in glioma-bearing patients: differential responses of peripheral blood mononuclear cells to stimulation with interleukin-2 and microbial antigen

Peripheral blood mononuclear cells (PBMC) of malignant glioma-bearing patients were stimulated in vitro with Interleukin-2 (IL-2) or a glucomannan-protein antigen of Candida albicans (GMP) then assayed for proliferation, production of IFN-gamma, and generation of cytotoxic effectors against either K562 tumor cell line or freshly-cultured allogenic glioma cells. PBMC of healthy, age and sex-matched subjects were the controls. PBMC of glioma-bearing patients did not differ, as a whole, from PBMC of healthy donors in IL-2 or GMP-induced proliferation. However, they showed a lesser ability to produce IFN as well as a substantial inability to generate cytotoxic effectors following GMP stimulation. PBMC of glioma patients were fully responsive to IL-2 in cytotoxicity generation, as were the PBMC from normal subjects. The results suggest that glioma patients may have a defective antigen-mediated activation of natural cytotoxic effectors. This hyporesponsiveness is not accompanied by depressed lymphoproliferation and does not apparently involve a reduced response to IL-2.

Mechanism of human interferon-gamma production: involvement of beta-2-microglobulin

The ability of several monoclonal antibodies (MoAbs) against beta-2-microglobulin (beta 2m) to inhibit interferon-gamma (IFN) production was assayed in peripheral blood mononuclear cells (PBMC). All of them strongly reduce IFN-gamma induction by galactose oxidase (GO), a well-characterized enzyme capable of activating T lymphocytes through mediation of macrophages. In contrast, many MoAbs directed against HLA class I (heavy chain) and class II antigens do not inhibit IFN induction by GO. On the other hand, anti-beta 2m MoAbs do not effectively reduce IFN-gamma induction by A23187, a calcium ionophore that acts on T cells in the absence of accessory cells. Competition experiments demonstrate that (i) the inhibition of anti-beta 2m antibodies was specific for beta 2m protein, and (ii) beta 2m is not itself the site of action of GO. Moreover, it is demonstrated that the addition of beta 2m to oxidated PBMC strongly enhances subsequent IFN-gamma production. Oxidation of galactose residues on glycoproteins of macrophage membrane is an obligate step for IFN-gamma induction whatever the inducer, thus our results suggest that beta 2m is involved in the mechanism of induction of IFN-gamma.

The response of peripheral blood mononuclear cells of glioma-bearing patients to stimulation with microbial antigen and IL-2: proliferation and IFN-gamma production

Peripheral blood mononuclear cells (PBMC) of malignant glioma-bearing patients were stimulated in vitro with a glucomannan-protein antigen of Candida albicans (GMP) or Interleukin-2 (IL-2), then assayed for proliferation and production of Interferon gamma. PBMC of healthy, age and sex matched subjects were the controls. PBMC from glioma-bearing patients did not differ, as a whole, from PBMC of healthy donors in IL-2 or GMP-induced proliferation. However, they showed a definitely lesser ability to produce IFN. The results are discussed in the framework of the impairment of immune responses known to affect glioma-bearing patients.

Influence of monoclonal antibodies against HLA class I and class II antigen on interferon-gamma and -alpha induction

The effects of several monoclonal antibodies (MAbs) directed against different epitopes of HLA class I and class II antigens on interferon (IFN)-gamma and IFN-alpha production were studied. The results indicate that: these MAbs have a marked inhibitory effect on the production of IFN-gamma induced by alloantigens and microbial antigens; they influence only to a lesser extent staphylococcal enterotoxin B (SEB)- and phytohemagglutinin (PHA)-induced IFN-gamma production; such effects parallel inhibition of lymphoproliferation except for PHA-induced blastogenesis, which is not affected; on the other hand, these MAbs have no effect on the production of IFN-alpha induced by lipopolysaccharide (LPS) or viruses.

Vitamin E supplementation in hemodialysis patients: effects on peripheral blood mononuclear cells lipid peroxidation and immune response

Lipid peroxidation and vitamin E levels in peripheral blood mononuclear cells (PBMC) were studied in 10 patients on maintenance hemodialysis. Significant increases of PBMC malonyldialdehyde (MDA) were detected, together with low vitamin E levels. After a fifteen-day-course of parenteral vitamin E supplementation, PBMC MDA reverted to normal values, while PBMC vitamin E levels remained lower than controls. In a parallel study an immunological monitoring was performed in the same patients before and after vitamin E supplementation. NK activity and PHA blastogenesis were not influenced by treatment, while a reduction of the number of OKT8+ lymphocytes were observed after vitamin E therapy. It is tempting to speculate that peroxidative damage of PBMC cell membranes in hemodialysis patients could, by impairing their functionality, influence immune responses and expression of functionally relevant membrane determinants.

Action of lysosomotropic amines on spontaneous and interferon enhanced NK and CTL cytolysis

Cell-mediated cytotoxicities, such as natural killer (NK) and T-dependent cytotoxic (CTL) activities, are inhibited to the same extent by lysosomotropic amines, even when interferon is added to cultures to enhance lysis. It is postulated that the amines block steps common to spontaneous and IFN-enhanced NK and CTL lytic mechanisms.

Interferon-induced augmentation of cytotoxic killer cell generation in mixed lymphocyte cultures: analysis of the effector cell product

Alloreactive cytotoxic lymphocytes were generated during mixed lymphocyte cultures (MLC). Human leucocyte interferon added during MLC gave rise to a moderate inhibition of thymidine uptake, yet augmentation of the allospecific cytotoxic product generated was found. Effector cell activities after MLC in the presence and absence of interferon against autologous cells were negligible, whereas NK-sensitive targets and antibody-coated target cells were killed to a higher extent, comparably, by cells generated during MLC in the absence of interferon. Cell separation experiments and cold target inhibition experiments were performed and showed that the effector cells generated with and without interferon had similar characteristics and were distributed among the same lymphocyte subpopulations. The key conclusion was that the augmented cytotoxicity was caused by alloreactive T cells, most of which were F(c) gamma receptor-negative, and was not due to enhanced 'NK-like' or antibody-dependent cell-mediated cytotoxic activity induced by interferon.

Interaction of GMI ganglioside with bovine serum albumin: formation and isolation of multiple complexes

The binding of ganglioside GM1 to bovine serum albumin has been studied by using absorption and fluorescence properties of the protein chromophores. Differences in the ultraviolet absorption spectrum and in fluorescence quenching, as well as a marked shift of the wavelength at the fluorescence maximum provide information about the binding of this ganglioside to albumin. Ultracentrifugal studies showed that there are two forms of the GM1-protein complexes which differ markedly in their molecular weight. These two forms have been separated on this basis, by a chromatographic sieving procedure, and designated as complexes I and II. Both complexes are characterized by a GM1: protein ratio of one ganglioside micelle per albumin polypeptide chain. Complex II polymerizes slowly and irreversibly to a dimer, complex I. These results have been correlated with the optical studies in order to draw limited inferences as to the environment of the binding sites on the native protein. The interaction between GM1 micelles and albumin is mostly hydrophobic and the two complexes are actually mixed ganglioside-protein micelles. At submicellar concentrations of ganglioside a binding of ganglioside GM1 to albumin also occurs. This process is due, however, to an aspecific, reversible adhesion of GM1 molecules on the albumin surface with no apparent perturbation of the albumin structure.