Serum interleukin 2 (IL-2) levels and prolactin bioactive/radioimmunoassay ratios of women at risk for breast cancer.

In a cohort of women at high risk for developing breast cancer we have observed that 74% of the women with prolactin BA/RIA ratios over 1.4 had detectable levels of IL-2 in their serum (990 +/- 400 mU/ml) and the IL-2 levels were correlated with the prolactin BA/RIA ratio (R = 0.79; P greater than 0.004). Women with BA/RIA ratios were either approximately 1.0 or less than 0.55 had lower levels of serum IL-2 (177 +/- 70 and 130 +/- 40 mU/ml, respectively). Detectable levels of serum IL-2 were found in 58% of those women with BA/RIA ratios of 1.0 and 55% of those with BA/RIA ratios less than 0.55.