SEASONAL EFFECTS OF ROTATIONAL STRESS ON LEWIS LUNG-CARCINOMA METASTASIS AND T-LYMPHOCYTE SUBSETS IN MICE

Rotational stress specifically increases the formation of spontaneous lung metastasis in mice bearing Lewis lung carcinoma, without signific antly modifying the growth of primary tumor. The increase in metastasi s number and volume caused by rotational stress varies in magnitude wi th a highly significant circannual rhythm; the acrophase approximately coincides with summer solstice. Rotational stress causes a significan t reduction in the number of CD3+ and CD4+ T-lymphocyte subsets in sum mer whereas in winter the number of CD3+ subset is significantly incre ased; the CD4+/CD8+ ratio and the number of NK 1.1 antigen positive ce lls are not significantly modified by rotational stress in both period s considered. The increase in metastasis formation by rotational stres s thus appears to negatively correlate with the number of splenic CD3 and CD4+ T-lymphocyte subsets. This seasonal behavior occurs in spite of the control of light cycle, temperature and humidity in the animal housing, suggesting the existence in the host of an endogenous oscill ator with a circannual period. These data indicate the opportunity to consider endogenous rhythms within the host, as well as seasonal facto rs, in studies on stress and neuroimmunomodulation in experimental onc ology.