Bernard Serrou

Human autologous rosettes: I. Mechanism of binding of autologous erythrocytes by T cells☆

Abstract A population of human peripheral blood lymphocytes is able to bind autologous erythrocytes in the presence of autologous serum. Erythrocyte binding is found to be more efficient at 4 °C after preincubation of lymphocytes in autologous serum for 30 min followed by overnight incubation. The overall cellular concentration and erythrocyte/lymphocyte ratio are also crucial in determining the weak erythrocyte binding to autologous lymphocytes. Membrane proteins are involved since the binding structures are sensitive to protease treatment. The 26% RFC obtained with an optimized assay are related to the T-cell lineage.

Increased sensitivity of IL2-dependent cultured T cells and enhancement of in vitro IL2 production by human lymphocytes treated with bestatin

Bestatin is an inhibitor of leucine aminopeptidase and aminopeptidase B which potentiates various immune functions, such as delayed hypersensitivity and antibody formation, and inhibits tumor cell growth in animal models. Our study focuses on the effect of Bestatin on interleukin 2 (IL2) sensitivity of IL2-dependent cultured T cells (CTC) and on IL2 production by human peripheral blood mononuclear cells (PBM). Bestatin (0.01 - 10 micrograms/ml) increases CTC 3H-TdR incorporation in the presence of suboptimal (low) concentrations of exogenous IL2. Bestatin alone has no mitogenic effect on CTC. This phenomenon is due to increased CTC IL2-receptors after treatment with Bestatin. Bestatin (1 - 10 micrograms/ml) also increases (1.4 - 21 fold) IL2 production by PHA-stimulated PBM. Bestatin therefore increases both IL2 sensitivity and IL2 production. This may explain the various immunopotentiating effects of Bestatin previously described.

Diminished interleukin-2 activity production in cancer patients bearing solid tumors and its relationship with natural killer cells

Interleukin-2 (IL-2) activity production by stimulated peripheral blood lymphocytes (PBL) from solid tumor bearing cancer patients was lower than in normal subjects. Natural-killer (NK) cell activity in the PBL of cancer patients was very significantly correlated to IL-2 activity production (P less than 0.001). These results might suggest a central role for IL-2 in the immune dysfunctions in cancer patients, and the possible use of IL-2 as an immunological response modifier in these patients.

Human autologous rosettes. II. Further characterization: markers and functions.

Abstract Purification of peripheral blood lymphocytes able to form autologous rosettes (ARFC) overnight has been obtained with satisfactory yield and enrichment, using short-term centrifugation on a Percoll cushion. Purified ARFC form E-rosettes, express human T-lymphocyte antigens, and contain cell-bearing Fc receptors for IgM but very few for IgG. They are also OKT4 positive. Morphological structure and cytochemistry (β-glucuronidase and acid phosphatase) do not suggest activation. The ARFC subset has poor antibody-dependent cell-mediated cytotoxicity and NK activity. They respond strongly to PHA and demonstrate a higher response in mixed allogeneic or autologous culture compared to non-ARFC or total PBL.

Modulation of human T lymphocyte functions by isoprinosine

Isoprinosine was shown to alter certain T cell functions. In vitro, it has previously been shown to induce suppressor cell activity in both mouse and human lymphocytes. Our in vitro results suggest that Isoprinosine acts on immune balance by increasing the number of non-suppressor T cells and, at least partially blocks Con A induced suppressor activity. In vitro NK activity remained unaltered.

The role of interleukin 1 and interleukin 2 in human T colony formation.

We investigated the roles of interleukin 1 (IL1) and interleukin 2 (IL2) on T colony formation by PHA-stimulated peripheral blood lymphocytes (PBL). Purified T cells stimulated by PHA could not generate T colonies as did PBL. Media conditioned by PHA-stimulated PBL (PHA-LCM) contained IL2 and a T colony-promoting activity (TCPA) which induced T colony formation in PHA-stimulated purified T cells. IL2 and TCPA are coeluted in the same peak of 18,000 molecular weight after gel filtration chromatography. Moreover, TCPA present in the PHA-LCM could be absorbed on IL2-sensitive cells which possessed specific receptors for IL2. These results suggest that TCPA and IL2 are related entities. Monocytes or IL1 (a monokine released by activated monocytes) also induced T colony formation in purified T cells. Phorbol myristate acetate (PMA) could replace monocytes in the induction of T colony. Monocytes, IL1, or PMA are known to be crucial requirements for IL2 production by PHA-stimulated T cells. This combined with the fact that IL2 participates in T colony formation suggests that monocytes induce T colony formation through IL2 production.

Human autologous rosettes. IV: Their relation with interleukin 2 activity production and natural killer cells in cancer patients

Peripheral blood lymphocytes (PBL) of solid-tumor-bearing cancer patients produced a lower interleukin 2 (IL-2) activity after lectin stimulation than did those from normal subjects. Moreover natural killer (NK) cell activity and autologous rosette forming (ARF) cell rate are found significantly correlated with IL-2 production in these patients. No direct relation is observed between ARF cell ratio and NK cell activity in a given patient. A central role for IL-2 in cancer patient immune dysfunctions is suggested. Two lines of pathogenetic mechanisms are documented. First, PBL exhibited cellular function defects, namely, autologous receptor expression, IL-2 production, and NK activity. Second, these dysfunctions involved, at least partly, plasma factors. The possibility of specific deficiency, (e.g., thymic factors) is not documented. Conversely it is demonstrated that patient plasma contain immunosuppressive factor(s) that block(s) IL-2 production and ARF cell expression. Involvement of ARF cell receptor in T-cell activation is discussed.

Induction of human T colony formation by phorbol myristate acetate.

Phorbol myristate acetate (PMA) is a potent inducer of T colony formation by peripheral blood lymphocytes. A mean cloning efficiency of 0.3% (0.05‐0.5%) is obtained with PMA concentrations of 100‐1000 ng/ml. PMA‐induced T colony formation does not require the presence of monocytes and therefore differs from other mitogens in this respect. Purified T‐colony‐promoting activity (TCPA) (devoid of phytohaemagglutinin (PHA)) increases PMA‐induced T colony numbers and induces T colony formation at low PMA doses (0.01 to 1 ng), concentrations at which no T colonies are detected in the absence of added TCPA. PMA‐induced colonies are mainly composed of cells bearing Fc receptors for IgM (54%), which is not the case for colonies obtained with PHA (11 %). PMA‐induced colony cells do not bind OKT3 and OKT4 monoclonal antibodies, whereas 23% are able to bind OK‐T8 antibody. These results demonstrate that PMA is a potent inducer of T colony formation and may therefore serve as a useful tool for the study of T‐cell differentiation.

Solubilization of a human lymphocyte factor for autorosette

With incubation at 45 degrees C, human peripheral blood lymphocytes (PBL) loose 80% of their capacity to form 1-hr autorosettes (AR). However, the addition of supernatant from heated lymphocytes (SHL) restores 93% of their rosette-forming capacity, while producing an inhibitory effect on nonincubated lymphocytes. A soluble factor present in SHL is active to a 1/5000 dilution; is absorbable on autologous red blood cells but not on sheep red blood cells; is RNase and DNase resistant and sensitive to trypsin and pronase; and acts variably on allogenic cells.

Stimulatory cells in the generation of T-cell-mediated cytotoxicity: potent stimulating activity of a small radioresistant spleen cell population (RSCs)

Abstract The combined effects of irradiation followed by cultivation on a total spleen cell population in order to study the evolution of the stimulating potential in the in vitro generation of allogeneic cytotoxic T lymphocytes (CTLs) were tested. Results revealed that, after 3 days and up to at least 7 days of cultivating irradiated (1000 rad) spleen cells, the remaining living cells (radioresistant spleen cells or RSC) have the same potential to generate CTLs as irradiated noncultivated spleen cells. RSC can resist a 5000-rad irradiation and induce a primary cytotoxic response pattern similar to that of total spleen cells; they act in primary as well as in secondary cultures with optimal responder to RSC ratios of about 100, but are still stimulatory at MLC ratios up to 1000 or 5000. They are lysed by specific allogeneic CTLs and readily inhibit the specific lysis of H-2-identical labeled targets by CTLs. RSCs do not express unusual levels of H-2 or Ia antigens and do stimulate purified T cells. Alloantisera anti-H-2 are able to completely block the RSC-induced generation of CTL. This RSC population may prove to be a good model to study non-H-2- or H-2-associated, nonserologically detectable determinants interacting in the generation of T-cell-mediated cytotoxicity.