Cellular immunity, also called cell-mediated, is an adaptive immunity in which lymphocytes of T type seek and attack diseased or foreign cells. The principal classification divides T lymphocytes into cytotoxic T (Tc), helper T (Th), regulatory T (Tr), and memory T (Tm) (Saladin, 2020). Tc cells are called the “effectors” – they attack foreign cells directly. Helper Th cells stimulate the action of Tc cells, simultaneously being responsible for their activation. After the pathogen’s defeat, Tc cells would remain bloodthirsty, continuing to produce inflammatory cytokines. In the long run, it can result in extensive tissue damage. Tr cells start inhibiting Tc’s cytokine secretion and multiplication, stopping the rampage. Finally, according to their name, Tm cells (descendants of Tc cells) are the cells responsible for cellular immunity’s memory. It is because of them people can become immune to certain diseases. Tm’s activation period is much faster than Tc’s one. Consequently, upon later reexposure to the same pathogen, Tm cells can mount a quicker response, dealing less overall damage to the host.
The mentioned four types present the generalized T cells classification. However, more sophisticated research equipment allows for a more thorough dissection of the T cell heterogeneity. Currently, at least 15 kinds of T cells are known in the medical field, with new ones being continually discovered (Jameson & Masopust, 2018; Saladin, 2020). Some of the subtypes possess unique qualities, such as, for example, Tscm cells. In contrast to their Tm counterparts, they showcase multipotency and long-term self-renewal capacity, making Tscm cells excel at long-lasting cellular immunity against microbial infections (acute and chronic) (Gattinoni et al., 2017). Nonetheless, their uniqueness can severely backfire in the case of immune-mediated diseases (Gattinoni et al., 2017). In other words, Tscm’s complex biology and extraordinary abilities present a double-edged sword for the host they are supposed to protect.
References
Gattinoni, L., Speiser, D. E., Lichterfeld, M., & Bonini, C. (2017). T memory stem cells in health and disease. Nature Medicine, 23(1), 18-27.
Jameson, S. C., & Masopust, D. (2018). Understanding subset diversity in T cell memory. Immunity, 48(2), 214-226.
Saladin, K. S. (2020). ISE anatomy & physiology: The unity of form and function (9th ed.). New York, NY: McGraw-Hill Education.