Effect of Time and Diet on the Immune Status of Mice Challenged with Herpes-transformed Cells

Human Herpes simplex virus type 2 (HSV 2)-transformed Balb/c mouse cells (H238 cells) are malignant in Balb/c mice. The immune stratus of mice bearing H238 cell-induced tumors was studied and changes in immune response with time and with altered diet of the mice were measured. In the experiments dealing with the status of immunity with time after tumor cell injection, mice were fed Purina Laboratory Chow (P.L.C.), injected with H238 cells, and sacrificed three to eight weeks post-injection. In the diet experiments, groups of mice were fed either P.L.C. or one of six equicaloric diets, consisting of low or high levels of protein (casein or soy) and low and high levels of fat for 15 weeks before injection of the tumor cells. Non-injected and 238 (non-transformed) cell-injected mice served as the controls. The weight of each mouse was determined weekly and the amount of food consumed per cage of mice was calculated twice each week. All of these mice were sacrificed eight weeks post-injection. Size of the right thigh of all H238 cell-injected mice was measured three times per week with vernier calipers at the greatest tumor diameter. At scarified each mouse and its spleen were weighed and relative spleen weights (R.S.W) were calculated. The spleen and lymph node cell were used in a microculture lymphocyte transformation test (LTT) using both phytohemagglutinin (PHA) and lipopolysaccharide (LPS) as mitogens. Stimulation indices (S.I.) were calculated using the means counts per minute (cpm) obtained from triplicate samples. Spleen cell differential counts (S.C.D.C.) were also performed on most of the diet mice. Statistical analysis was done on the results with the use of a computerized Student\u27s T test to determine significant difference (P values). Great increases in spleen size were noted in all mice with progressive tumor, especially from three to five weeks and again from seven to eight weeks post-injection. In progressor mice the spleen cell PHA-S.I.s steadily decreased from near-normal values at three weeks (~ 51) to markedly depressed values (\u3c 10) by eight weeks. In the regressor and no-visible-tumor mice, this depression was not noted. When lymph node cells were tested, the mean PHA-S.I. was significantly elevated at four weeks post-injection, while the means obtained at all other weekly intervals were similar to the control values. The response of both spleen and lymph node cells to LPS was depressed early after tumor cell injection in mice with progressive tumor, but recovered and leveled off to normal values by eight weeks. Striking differences were observed in the incidence of tumors in the mice fed the various diets and P.L.C. All of the mice fed the high-soy protein diet and 97.5 percent of those fed P.L.C., in which the protein was mainly derived from meat, developed progressive tumors while only 55 - 60 percent of mice fed the two low-fat, casein, diets did so. Percent values for the other diet mice were intermediate. In addition. it was noted that progressor mice on the casein, low-fat diets had the longest latent period before tumor appearance and smallest tumor size at sacrifice. Progressor mice fed the casein, low-fat diets had the lowest mean R.S.W.s and the least variation from normal in the S.C.D.C. pattern, although an increase in the percent of mature granulocytes was seen in all mice with progressive tumor. Analysis of the cpm obtained during the LTT revealed that both spleen and lymph node cells of these mice were more active than those of any of the other groups in the presence or absence of PHA. A three to four-fold higher mean spleen cell PHA-S.I. was also seen in the casein-fed mice when compared to those obtained for progressor mice fed the low-fat, soy protein diets and P.L.C. The degree of depression in spleen cell PHA response in these mice was lower than that of any of the other groups. Also, these mice were the only ones to show an increase in lymph node cell responsiveness to PHA with an increasing tumor load. Humoral immunity appeared to be affected more by level rather than type of protein. Progressor mice fed the high-casein, low-fat diet had a significantly enhanced spleen cell response to IPS when compared to that of mice fed the low-casein, low-fat diet. In addition, progressor mice fed the low-soy protein, low-fat diet had a significantly higher lymph node cell response to LPS than those fed the other two soy protein diets. In mice on each of the diets and P.L.C. a range of weight gains was observed. However, body weight gain did not have a significant effect on tumor production by injection of H238 cells or on any of the parameters tested. In summary, cell-mediated immunity was increasingly depressed with time in mice with progressive H238 cell-induced tumors. Humoral immunity was depressed early after tumor cell injection, but later recovered. The results of the experiments involving diet showed than the type, in comparison to level, of protein had more effect on tumor development and immune function in the H238 tumor system, although high-soy protein did increase tumor incidence over low-soy protein. In addition, it appears that casein exerted an antitumor effect which may have been due to enhancement of cell-mediated immunity. Conversely, meat and soy protein appeared to depress cell-mediated immunity and enhance tumor development. A high level of fat was tumor-enhancing when used together with casein but tumor-inhibiting when used with soy protein