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Lymphocytes in peritoneal exudate from BALB/(c) mice immunized against ascites leukemia EL4 are uniquely efficient at destroying (51)chromiumlabeled EL4 cells in vitro. The lytic process depends upon the number of lymphocyte-tumor cell interactions. Efector lymphocytes are not inactivated as a result of lethal contact but can interact repeatedly with tumor cells.

A pathway for cell-mediated tumor destruction in vitro by immune peritoneal exudate lymphoid cells has been proposed. The union of lymphocytes and tumor cells precedes the formation of an intermediate phase leading to lysis. The initial interaction is only partially temperature dependent. The cytolytic process per se is highly temperature dependent, being negligible at 25 degrees C but proceeding rapidly at 37 degrees C. (51)Cr release from tumor cells is demonstrable within 10 min at 37 degrees C and can be reversibly arrested by cooling. Once initiated, lysis is largely independent of additional interactions and continues at almost full rate for 30 min. The effector cells are not lysed and appear to be free to enter into further effector cycles.

Peritoneal exudate cells (PEC), obtained after the rejection of EL4 leukemia by BALB/c mice, are much more effective in the specific in vitro destruction of (51)Cr-labeled EL4 cells than are spleen, thymus, lymph node, or peripheral blood lymphocytes. The presence of a large number of effector cells at the site of graft rejection is reflected in the potent cytolytic activity seen in vitro. Effector cells temporarily lose cytolytic reactivity when treated with trypsin but regain reactivity with time. This recovery occurs in normal as well as in immune serum. The destructive reactivity of PEC is increased when macrophages are removed. The remaining population of nonadherent PEC is composed primarily of small- to medium-sized lymphocytes. Complex tissue culture media are not needed, but there is a definite requirement for serum. The required serum component is heat stable, nondialyzable, and is not consumed during the reaction. The use of an ascites allograft system made these observations possible and permitted the isolation of those host cells intimately associated with rejection.

The normal variations in the paper electrophoretic lipoprotein patterns in 240 healthy Canadian males and females, aged 10 to 59 years, have been described and compared with serum cholesterol and triglyceride levels.The incidence of abnormal chylomicra, beta and pre-beta lipoproteins was similar in both sexes and increased with age in both sexes.Chylomicron bands and/or pre-beta trails from the origin occurred in 4% of subjects, pre-beta bands in 27% and "abnormally" dense beta bands in 28%.Five per cent of subjects were considered to have definite hyperlipoproteinemia, another 19% had slight and 21% had questionable hyperlipoproteinemia. Fifty-five per cent were normal.