Recently, some investigators have reported blunted natural killer cell activity (NKCA) in patients with major depression. In addition, there were some reports on negative relationships between NKCA and the occurence of negative life events. In order to replicate the above findings, the present study investigates NKCA and negative life events in 11 normal and 35 unipolar (minor, simple major, melancholic) depressed subjects. NKCA has been determined by all subjects. They completed the Questionnaire on Recently Experienced Events with scores on number and impact factor of events related to a) illness, b) working conditions, c) social relationships, d) housing problems, e) loss of possession. Depressed subjects reported higher scores on number and/or impact factor of events related to illness, social relationships and housing problems. In our investigation NKCA was significantly blunted in depressed subjects and, particularly in melancholies. So NKCA is negative correlated to the severity of depression. We were unable to detect any significant relationship between NKCA, and life events ( number of impact factors ), Our results do not corroborate the thesis that life events may affect immune function, as assessed by NKCA.

Previously, we showed that mice fed white button mushrooms (WBM) had enhanced immune functions known to help the body's antiviral defence. In the present study, we tested whether WBM conferred protection against viral infection. Young (4-month-old) and old (22-month-old) C57BL/6 mice were fed a diet containing 0, 2 or 10 % WBM powder for 8 weeks. Mice were then infected with influenza Puerto Rico/8/34 (H1N1), and killed at day 0 (uninfected), 2, 5 or 7 post-infection. The primary outcomes of the study were viral titre and body weight. Secondary outcomes were natural killer (NK) cell activity, lymphocyte proliferation and cytokine production. The results showed that WBM did not affect viral titre, nor did it prevent infection-induced weight loss. WBM supplementation was found to enhance NK cell activity in old mice and to increase interferon (IFN)-γ production in young and old mice under naive (uninfected) conditions, but it had no such effect after infection. The lack of a mushroom supplementation effect on NK activity and concanavalin A-stimulated IFN-γ production after infection may explain the immune system's failure to reduce viral load and weight loss in mice after influenza infection. WBM supplementation, however, did induce changes in other aspects of the immune response: it significantly increased the production of T-helper type 2 cytokines IL-4 and IL-10 in uninfected mice and pro-inflammatory cytokines IL-1β and TNF-α in infected mice. These mushroom-induced systemic changes, however, were not adequate to confer a protective effect against influenza infection.