Brief naturalistic stressors (such as exams) tended to suppress cellular immunity while preserving humoral immunity. Chronic stressors were associated with suppression of both cellular and humoral measures
The more a stressor deviated from those parameters by becoming more chronic, however, the more components of the immune system were affected in a potentially detrimental way.
https://doi.org/10.1016/j.ejon.2003.09.003
https://doi.org/10.1080/16506078809455814
https://doi.org/10.1037%2F0033-2909.130.4.601