Showing papers by "Wolf H. Fridman published in 1977"

Human virus-infected target cells lacking HLA antigens resist specific T-lymphocyte cytolysis.

Abstract: PRODUCTS of the major histocompatibility complex (MHC) are important as target structures in T lymphocyte-mediated cytolysis. In mice, virus (or hapten)-sensitised T cells are cytotoxic for specific virus-infected (or hapten-modified) target cells exclusively when syngeneic or at least identical for either the K or D region of the MHC1–5. These findings led to the ‘altered-self’ hypothesis6 which assumed that cytotoxic T cells do not recognise specific viral antigens, but rather a modification of histocompatibility antigens induced by the viral infection. One prediction of this theory was that murine cells expressing viral antigens but lacking H–2 determinants would be resistant to T cell-mediated lysis. Indeed, this fact was established recently by Zinkernagel and Oldstone using murine F 9 teratoma cells7. There is still no evidence for the involvement of HLA antigens in the process of immune killing of virus-infected target cells by human T lymphocytes. But, Svedmyr and Jondal have shown that peripheral T cells from patients with infectious mononucleosis (IM)—and not from normal donors—killed specifically Epstein–Barr virus (EBV) genome-carrying B lymphoblastoid cell lines8 and Burkitt's lymphoma cells9. By contrast, these T cells were devoid of any cytotoxic activity against EBV negative cell lines. Similar data were obtained by other workers10,11. Thus, peripheral T cells from patients with infectious mononucleosis seemed to be sensitised to viral coded determinants, and could presumably be used in a model to study T-lymphocyte killing of virus-infected cells in human. If, in man as well as mouse, the MHC is directly involved in the target structure recognised by virus-sensitised cytolytic T lymphocytes, HLA-lacking target cells should be resistant to immune T-ceil killing. We report here that Daudi cells, originating from a human Burkitt's lymphoma line and lacking HLA products12–14, are resistant to lysis by EBV-sensitised peripheral T lymphocytes from patients with infectious mononucleosis.

The role of the Fc receptor (FcR) of thymus-derived lymphocytes. II. Presence of FcR on suppressor cells and direct involvement in suppression.

Abstract: Alloantigen-activated T cells (ATC) were prepared by injecting C3H/He thymocytes into host-irradiated BALB/c mice. ATC were taken from the spleen of the recipients at day 5 and tested for their activity on “In vitro” primary antibody production to sheep red blood cells (SRBC) induced in splenic C3H/He lymphocytes. ATC added 24 h after antigen were found to be suppressive. Separation of ATC by velocity sedimentation, according to cell size showed that suppressor cells were found in each population, medium and large lymphocytes, however, being more active. Separation of ATC, according to the presence of Fc receptor (FcR) at their membrane was achieved by velocity sedimentation after rosetting with IgG-sensitized SRBC (EA). Suppressor cells were then found in FcR+ and not in FcR− fractions, the degree of suppression being parallel to the ratio of FcR+ cells. At both extremes, pure populations of FcR+ cells were highly suppressive, while populations of ATC, completely devoid of FcR+ cells, were inactive. Since FcR is a very labile molecule at the T cell surface and shed within 3 h at 37°C, but not at 4°C, ATC were pre-incubated at each temperature and added 24 h after antigen to the spleen cell cultures. In these cases, ATC having released their FcR, were much less suppressive than control ATC, and in previous work we have shown that the suppressive activity was found in the cell supernatant associated with an FcR-like molecule (immunoglobulin-binding factor). The data therefore allow the conclusion that FcR may be a marker of nonantigen-specific suppressor T cells and seems to be involved itself in the suppression phenomenon.

Binding Site of Human IgG Subclasses and Their Domains for Fc Receptors of Activated Murine T Cells

Abstract: A subpopulation of activated murine T cells (25%) were found to bear Fc receptors for mouse, rabbit, and human IgG. Studies, by rosette inhibition and indirect immunofluorescence, of their specificity for human IgG subclasses have shown that these receptors bound nonaggregated IgG1, IgG2, and IgG3 in a comparable fashion, but did not bind IgG4. The binding site has been localized exclusively to the Fc region and the binding capacity of this fragment was not affected by mild reduction. Binding of the Fc fragment of IgG4 could not be demonstrated. Using isolated Cγ2 and Cγ3 (pFc′) domains from IgG1 and a Cγ3-derived fragment (Fc′), a major binding site was localized to the Cγ3 domain between residues Gln 342 and His 433 . A 10-fold molar excess of Cγ3 dimer over native Fc was, however, required to show comparable activity. The monomeric Cγ2 domain was 10-fold less active than the Cγ3 fragment. Human urine β2-microglobulin was not cytophilic. These data are discussed and it is suggested that the Cγ2 and Cγ3 domains may contribute to the formation of a cooperative binding site through quaternary interdomain interactions. By redistribution experiments, it was demonstrated that the three human IgG subclasses shown to be cytophilic share common or linked receptors, which were not associated with the H-2 alloantigens.

Characterization of suppressive immunoglobulin-binding factor (IBF). II. Purification and molecular weight determination of IBF produced by L-5178-Y theta-positive lymphoma.

Abstract: L-5178-Y thymoma cells were used to produce radioactive immunoglobulin-binding factor (IBF). For this purpose, the cells were internally labeled by incubation with radioactive amino acids and/or fucose. The supernatants contained radioactive material that bound to IgG-sensitized erythrocytes and suppressed the in vitro antibody response to sheep red blood cells. Upon filtration on Sephadex G-200 both the IgG-binding activity and the suppressive activity eluted at peaks of 140,000 and above 300,000 d. However, on SDS polyacrylamide gels, after precipitation with antigen-IgG-antibody complexes, IBF was found in a single peak of 80,000 d. This molecule could be dissociated in the presence of mercaptoethanol into a major unit of 40,000 d and a minor unit of 20,000 d. These data suggest that IBF is a molecule of 80,000 d, which contains chains of 40,000 d and probably 20,000 d linked by disulfide bridges. In cell supernatants, however, the factor exists in polymeric forms of 140,000 d and more than 300,000 d.

Characterization of suppressive immunoglobulin-binding factor (IBF). I. Production of IBF by a theta-positive lymphoma (L-5178-Y).

Abstract: L-5178-Y, a θ-positive, Fc receptor-bearing mouse thymoma cell line spontaneously releases immunoglobulin-binding factor (IBF) upon short-term incubation in vitro . IBF produced by L-5178-Y cells is identical in its biologic activity with IBF produced by Fc receptor positive alloantigen-activated T cells. It suppresses the in vitro plaque response of mouse spleen cells to sheep erythrocytes by interfering mainly with the late phase of the generation of antibody-forming cells. Therefore, L-5178-Y thymoma affords a homogeneous source of IBF in sufficient quantities for the study of its biochemical nature and the mechanism by which it interferes with cells participating in antibody synthesis.

The role of the Fc receptor (FcR) of thymus-derived lymphocytes. I. Presence of FcR on cytotoxic lymphocytes and absence of direct role in cytotoxicity.

Abstract: Cytotoxic T lymphocytes (CTL) were prepared by injecting C3H/He (H-2k) thymocytes into host-irradiated BALB/b (H-2b) mice. Specific cytolysis was measured on MBL2 lymphoma cells from C57BL/6 (H-2b) mice. Alloantigen-activated T cells (ATC) were taken from the spleens of the recipients at day 5 and separated according to size and/or to the presence of membrane Fc receptors (FcR) by the use of velocity sedimentation techniques. The data showed that CTL were found in populations of lymphocytes heterogeneous in cell size and were always present in the FcR-positive population. Depletion of FcR-positive ATC, after rosetting with IgG-sensitized sheep erythrocytes led to an abolishment of cytolytic activity while enrichment in FcR-positive ATC led to a parallel increase of cytolytic activity. Taking advantage of the rapid release of FcR at 37°C by ATC, we investigated the direct involvement of the FcR molecule in cytolysis. We found that ATC which had released their FcR after pre-in-cubation for 2 h at 37°C exerted the same level of cytotoxicity as control ATC incubated at 4 °C. The data lead us, therefore, to conclude that FcR may be a marker of differentiation of cytotoxic T cells found in the spleen, but does not itself play a role in the cytolytic reaction.