Periodicity of susceptibility to pneumococcal infection: influence of light and adrenocortical secretions.

Circadian periodicity of susceptibility to pneumococcal infection was altered but not abolished in blind or adrenalectomized mice. Serum corticosterone concentrations 24 hours after pneumococcal challenge were greatest in animals challenged at 0400 hours, a time when circulatory corticosterone is lowest; the smallest absolute increase in serum corticosterone followed challenge at 1600 hours.