Cytotoxic potential of lymphocytes stimulated with autochthonous lymphoid cell line cells

Stimulation of lymphocytes by allogeneic lymphocytes and lymphoblasts in the presence of anti-HLA antisera

Anti-HLA alloantisera inhibit mixed lymphocyte responses in which normal lymphocytes are used as stimulator cells. These same antisera are unable to inhibit lymphocyte proliferative responses stimulated by lymphoblastoid cells from cultured lymphoid cell lines. They also fail to inhibit either the generation of cytotoxic effector cells by lymphoblastoid cells or lymphocyte-mediated cytotoxicity against the lymphoblasts. Although the number of HLA antigens on the surface of lymphoblasts is reported to be greater than on normal lymphocytes, the failure of alloantisera to inhibit lymphoblast-induced responses in vitro does not appear to be due to insufficient amounts of antiserum to react with the antigenic sites. Rather, the data are interpreted to suggest that antigens which are not HLA and are not closely associated with HLA on the lymphocyte membrane are responsible for the stimulation of allogeneic lymphocytes by lymphoblastoid cells. Although lymphoid cell lines are known to contain the genome of the Epstein-Barr virus, antisera against products of the viral genome fail to inhibit proliferative responses to lymphoblastoid cells, suggesting that these antigens do not directly participate in lymphocyte activation.

Cell-mediated immunity to Epstein-Barr-virus-transformed lymphoblastoid cells in acute infectious mononucleosis

Mononuclear peripheral blood leukocytes from 21 patients with infectious mononucleosis and 16 healthy controls were tested in a 51Cr-release assay for cytotoxicity against two human lymphoblastoid cell lines derived from the same donor. One line contained the Epstein-Barr virus (EBV); the other did not. Acute-phase leukocytes were significantly more cytotoxic against the EBV-infected cell line than were control leukocytes. Mean (+/- S.E.) lysis at a leukocyte-target-cell ratio of 100:1 was 10.6 +/- 1.6 per cent for patients and 3.4 +/- 0.6 per cent for controls (P less than 0.0005). Cytotoxicity correlated with the percentage of atypical lymphocytes. Cells of three patients with acute mononucleosis-like illnesses failed to show killing activity above those of normal controls. Cytotoxicity against the EBV-negative line was not significantly different for each group. The finding of cytotoxic cells in infectious-mononucleosis patients with atypical lymphocytes suggests that these cells operate in vivo to limit the proliferation of altered EBV-transformed B lymphoblasts.

Infectious mononucleosis: model for self-limiting lymphoproliferation

Evidence for the extensive lymphoproliferation which characterises infectious mononucleosis (I.M.) is summarised, and some of the mechanisms which are though to control lymphoproliferative activity in this disease are discussed. The main host responses which appear to limit lymphoproliferation in I.M. include the development of humoral antibodies against the Epstein-Barr (E.B.) virus-associated membrane antigen (present on the E.B. viral envelope and on E.B.-virus-infected cells) and cellular immune responses directed against E.B.-virus-containing lymphocytes. Recent evidence is reviewed which indicates that E.B. virus preferentially infects B lymphocytes and that these E.B.-virus-containing cells, which are altered antigenically, evoke a massive response in the host T cells which do not carry E.B. virus; in the presence of E.B.-virus-infected B cells, T cells are transformed and become cytotoxic for B cells. Some of the general implications of the predominant T-cell response in I.M. are discussed with particular relation to autoantibody formation and antigenic competition. The possible role of the distinctive heterophil antigens and antibodies in determining the self-limiting course of I.M. is briefly considered. The general status of I.M. as a self-limiting, albeit intense, lymphoproliferative disease is appraised and the tenuous relationship between I.M. and irreversible lymphoproliferative states is discussed.