Kinetics of the reactivity of subpopulations of spleen cells of mice bearing virus-induced mammary tumors to syngeneic antigenic extracts in vitro. Supportive and suppressive effects of macrophages

Effects of the removal of adherent and phagocytic cells on the spleen cell lymphoproliferative response of tumor-bearing mice

Cell-mediated immunity was investigated in two BALB/c mouse tumor systems using the lymphoblastogenesis test with phytohemagglutinin as the mitogen. This lymphoproliferative response was quantitated using the Stimulation Index (SI). There was little evidence for suppressor cell activity in cell mixing experiments in which spleen cells from #51 cell-injected mice were mixed with spleen cells from normal mice. Following macrophage removal by Sephadex G-10 columns and carbonyl iron ingestion, there were no significant changes in the SI values for spleen cells from the #51 cell-injected mice. In contrast, spleen cells from mice injected with H238 cells, a herpes virus-transformed cell line, had a significantly lower SI value than that of normal mice. Suppressor cell activity was demonstrated in cell mixing experiments in which spleen cells from H238 cell-injected mice were mixed with normal spleen cells. Removal of adherent cells from spleen cells from H238 cell-injected mice by Sephadex G-10 columns restored the SI value to that of normal mice. An increased SI value was also seen after removal of phagocytic cells by carbonyl iron. These results suggested that cells with the functional properties of macrophages played an important part in the immunosuppression observed in the H238 tumor system. Comparison of the two macrophage depletion methods suggested that another cell population was also involved in the suppressive effect. Results of immunofluorescent techniques with anti-Lyt-1 and anti-Lyt-2 monoclonal antibodies show these cells to be Ly 1-, Ly 2,3+ phenotypes of T-lymphocytes.

Serial evaluation of absolute spleen cell numbers in Lewis lung tumor-bearing mice

Subcutaneous (sc) transposition of the spleen followed by fine needle biopsies (FNB) from the organ allows the evaluation of relative numbers of splenic cells in Lewis lung tumor-bearing mice. Absolute cell numbers (N) can be calculated when the aspirated cells are weighed on a precision balance (m) and counted (c) after resuspension in a defined volume (v): N = C X V/m X M. The weight from the whole spleen (M) is derived from a calibration curve. Splenic nucleated cells and their subsets--as determined by the use of monoclonal antibodies--can thus probably be evaluated with a degree of accuracy which was not possible before. Shifts of splenic cells from and to the organ can be monitored.

Normal and tumor-bearing host macrophage factor-mediated modulation of mixed-lymphocyte reaction responsiveness: separation of T-lymphocyte subset susceptibility to enhancing and inhibitory factors

The mixed-lymphocyte reaction reactivity of normal and tumor-bearing host (TBH) T-cell subsets was examined in response to normal and TBH macrophage (M phi) supernatants. Both inhibiting and enhancing activities were identified in normal and TBH M phi supernatants. The present data suggest that TBH M phi supernatants contained more inhibitory activity than normal host M phi supernatants and that enhancing activity of M phi supernatants was restricted to the Lyt 2,3+ population of cells. TBH Lyt 2,3+ cells were more responsive to the enhancing molecule(s) than their normal counterparts. These data were consistent with studies which implicate M phi as being partially responsible for the immune dysfunction seen in TBH, and extends previous findings on the ability of M phi to regulate the immune response in an attempt to achieve homeostasis.

Macrophage depletion and manipulation of enhanced immune response in an animal model of bladder cancer

In a transplantable model of bladder cancer the inhibition of tumor growth by polyinosinic:polycytidylic acid (poly(I:C], concomitant stimulation of natural killer cell activity, and inhibition of both effects by prior inoculation with anti-interferon antiserum have been previously observed. The possible role of macrophages in these interactions is explored. Depletion of peritoneal macrophages by silica at concentrations that did not markedly depress natural killer cell activity was found to inhibit the enhancement of natural killer cell activity by subsequent in vivo poly(I:C) inoculation. Inoculation with silica also seemed to abrogate the tumor inhibitory effect of poly(I:C) treatment. To determine whether effects of poly(I:C) on natural cytotoxicity and tumor growth were mediated through production of interferon, anti-interferon antiserum (alpha-IF) was inoculated prior to poly(I:C) therapy. Tumor growth appeared to be uneffected by this maneuver even though poly(I:C)-induced enhancement of natural cytotoxicity was inhibited. Taken together, both macrophages and interferon may play a pivotal role in the immune response in both a stimulatory and a suppressive capacity. Additional study on such influences may be important if in vivo manipulation of these regulatory effects is to be accomplished successfully.

Reactivity of subpopulations of mouse spleen cells to concanavalin A in vitro

Subpopulations of spleen cells of mice bearing virus-induced mammary tumors were assessed for responsiveness to Concanavalin A (Con A) under in vitro xenogeneic and syngeneic culture conditions. When cultured with human A+ plasma (xenogeneic), spleen cells of normal, nontumor-bearing BALB/c mice exhibited a high degree of synthesis as compared to unstimulated cells in response to Con A. Spleen cells of mice inoculated with tumor exhibited response exceeding that of their normal counterparts by 59%. When normal BALB/c sera (syngeneic) was used as the supplement, no response of normal spleen cells was observed upon stimulation by Con A; however, spleen cells from tumour bearing individuals demonstrated heightened activity. Tumor-bearer spleen cell response to Con A of mice inoculated with 1 X 10(6) viable cells was biphasic. The peak of the first phase appeared as early as 10 days postinoculation and declined within 3 days after its appearance. The peak of the second phase appeared within 6 days following decline of the first and declined drastically within 3 days after its appearance. Coincidental with the onset of the second phase, the tumor became ulcerated, purulent, and necrotic. Both phases were predominantly T-cell mediated.