For example, studies of medical students facing examinations and kindergarten children beginning school reveal changes in immune functioning potentially prognostic for adverse health outcomes, including changes in numbers of total t - lymphocytes, natural
killer cell cytotoxicity, and lymphocyte responsivity to mitogenic stimulation (e.g., 8, 9).
The systemic effects of stress include increased levels of stress hormones such as cortisol, a decline in certain aspects of immune system function such as natural
killer cell cytotoxicity or secretory - IgA levels, and a disruption of gastrointestinal microflora balance.