Characterization of immunological depression in mice exposed to normobaric oxygen.

Immunological cell functions were evaluated during 24, 48 and 96 h O2 exposure in C57Bl/6 mice. A normobaric O2 exposure resulted in depression of delayed type hypersensitivity (DTH) to oxazolone and Staphylococcus aureus antigens. This effect was proportional to the duration of O2 exposure. The antibody response of splenic cells was more rapidly (24 h O2 exposure) and markedly depressed using a T-dependent antigen (sheep red blood cell, SRBC) than with a T-independent antigen (trinitrophenylated lipopolysaccharide, TNP-LPS). While mitogen-induced proliferative responses of spleen cells to Con A and PHA were inhibited after 72 h of O2 exposure, proliferative responses to LPS were inhibited after 96 h. A dissociated antigen and mitogen responses was observed after a short time of O2 exposure (48 h): the antigen specific responses were impaired with a more pronounced effect on T lymphocytes, whereas the DNA synthesis in response to mitogen remained normal.