- Neutrophilia (high blood neutrophilia counts) and lymphopenia (low blood lymphocyte counts) are induced by high plasma levels of stress hormones such as epinephrine and cortisol.
- There is decrease in the delayed-type hypersensitivity response, a complex immunological process that involves several different cell type (including T lymphocytes) and chemical mediators and is manifested by firm, red skin indurations.
- Plasma concentration of pro- and anti- inflammatory cytokines (e.g., interleukin–6, interleukin-10, and interleukn-1 receptor antagonists) are increased. Cytokines are low-molecular-weight proteins and peptides that help control and mediate the interactions among cells involved in immune responses. Prolonged and intensive exercise bouts induce muscle cell injury, causing a sequential release of pro- and anti- inflammatory cytokines.
- Nasal and salivary immunoglobulin – A concentration, nasal mucociliary clearance, and nasal neutrophil function are decreased. This indicates an impaired ability of the upper respiratory tract to clear external pathogens.
- Major histocompatibility complex (MHC)-II expression and antigen presentation in macrophages are blunted. The MHC antigens are essential for reactions of immune recognition. After phagocytosis and antigen processing, small antigenic peptides are bound to MHC II and presented to T lymphocytes, an important step in adaptive immunity. These data imply that heavy exertion can blunt macrophage expression of MHC II, negatively affecting the process of antigen presentation to T lymphocytes and thus their ability to respond to a challenge from viruses.