It was found that inoculation of several strains of mice with several types of
tumor cells resulted, within 24 hr, in a significant decrease in the serum
leucogenenol levels of the mice. Serum
leucogenenol levels of the mice inoculated with
tumors that are rejected become normal or temporarily above normal at approximately the time the
tumor is observed to be rejected. Contrariwise, serum
leucogenenol levels of mice inoculated with
tumors that are not rejected remain at significantly lower than normal levels during the life of the mice. Unlike
tumors, skin allografts increase serum
leucogenenol levels. When
tumors are rejected because of the previous immunization of the mice, serum
leucogenenol levels become normal at approximately the time the
tumor is observed to be rejected. Excision of the
tumor after 1 week of growth, with the consequent recovery of the mice, is accompanied by a recovery of normal serum
leucogenenol levels. Also, it was found that injection of mice with a cell-free
0.9% NaCl solution extract of a
tumor results in a temporary decrease in serum
leucogenenol levels comparable to that observed with the inoculation of a viable
tumor which lasts from 24 to 96 hr. It is suggested that the suppression of serum
leucogenenol levels is one of the factors responsible for the immunosuppression associated with a growing
tumor.