Several cytokines including gamma-interferon, tumor necrosis factor alpha, interleukin 1 beta (IL-1 beta), and interleukin 6 (IL-6) are pyrogenic and can inhibit lipogenic processes. Because patients with lymphoma often suffer from fever, weight loss, and night sweats (B symptoms), the etiology of which is unknown, the authors investigated serum levels of these cytokines in normal volunteers and in patients with Hodgkin's and non-Hodgkin's lymphoma. Sixty serum samples from patients with Hodgkin's disease (28 patients) or non-Hodgkin's lymphoma (32 patients), as well as 20 samples from normal volunteers, were collected. The majority of patients had advanced (Stage III or IV) or relapsed disease. The assay for gamma-interferon was a specific and sensitive radioimmunoassay (lower limit of detection = 0.1 unit/ml); the assays for tumor necrosis factor alpha, IL-1 beta, and IL-6 were enzyme-linked immunoassays with lower limits of sensitivity of 10 pg/ml, 20 pg/ml, and 22 pg/ml, respectively. There were no statistically significant differences in gamma-interferon, tumor necrosis factor alpha, or IL-1 beta levels between lymphoma patients and normal subjects. In contrast, 20 of 57 patients (35%) with lymphoma as compared with 0 of 19 normal volunteers (0%) had detectable serum IL-6 levels (P < 0.005, chi 2 test). Interestingly, 17 of 29 lymphoma patients with B symptoms (59%) as opposed to 3 of 28 lymphoma patients without B symptoms (11%) had detectable serum IL-6 levels (P < 0.001, chi 2 test); the median IL-6 level was 28.9 pg/ml (B symptoms present) versus undetectable (no B symptoms) (P < 0.005, Mann-Whitney U test). Analyzing Hodgkin's and non-Hodgkin's lymphoma groups separately revealed similar results. IL-6 levels showed no significant correlation with time from diagnosis, beta 2-microglobulin, or lactate dehydrogenase levels. However, analysis by the method of Kaplan and Meir demonstrated that the median survival of Hodgkin's disease patients with detectable IL-6 levels (> or = 22 pg/ml) was 10 mo, whereas the median survival has not been reached at a median follow-up time of 37.5 mo in those patients with lower values (Wilcoxon P value = 0.0012). There were too few patients in each subset of non-Hodgkin's lymphoma to determine the correlation between IL-6 and survival but, considered as a single group, a statistically significant correlation was not found.(ABSTRACT TRUNCATED AT 400 WORDS)