Which cells are activated in cellular immunity to destroy intracellular pathogens?

• A. B Cells
• B. Cytotoxic T Cells and NK Cells
• C. Plasma Cells
• D. Eosinophils

Answer: (B)

Cellular immunity works by killing cells that have been invaded, so the body stops the pathogen from replicating inside those cells. The main effectors are cytotoxic T lymphocytes, which recognize viral or intracellular pathogen peptides displayed on MHC class I molecules on infected cells. When they find a match, they unleash perforin and granzymes to induce apoptosis of the infected cell, halting the pathogen’s spread. Natural killer cells also play a key role here by targeting cells that show abnormal or reduced MHC I or other stress signals, delivering a rapid cytotoxic hit to destroy those infected or damaged cells.

In contrast, B cells and their mature form, plasma cells, drive humoral immunity by producing antibodies that circulate outside cells to neutralize extracellular pathogens and toxins—not by directly killing infected host cells. Eosinophils are more involved in fighting parasites and mediating certain allergic responses rather than removing intracellular pathogens.

Thus, cytotoxic T cells and NK cells are the principal players activated in cellular immunity to destroy intracellular pathogens.