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How do B cells and T cells respond to an infection?

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B cells and T cells are essential components of the adaptive immune system that work together to eliminate pathogens. They respond to infections through distinct but complementary mechanisms:12

B Cell Response (Humoral Immunity)

B cells primarily target pathogens residing outside of body cells.2
* Activation: A B cell is activated when its surface receptors bind to a specific antigen. Most B cells require additional stimulation from an activated helper T cell to fully differentiate.34
* Clonal Expansion: Once activated, B cells multiply into clones.34
* Differentiation: They develop into plasma cells, which secrete large quantities of antibodies into the blood and lymph to neutralize or destroy the invader. Some B cells become memory B cells, which persist for years to provide a rapid, stronger response upon reinfection.342

T Cell Response (Cell-Mediated Immunity)

T cells focus on eliminating pathogens that have bypassed antibody defenses by entering body cells.52
* Helper T Cells: These cells coordinate the immune response by secreting cytokines, which activate B cells and enhance the activity of other immune cells like macrophages.15
* Cytotoxic T Cells: These cells directly destroy infected or abnormal cells by triggering apoptosis or using pore-forming molecules to kill the target.15
* Memory T Cells: Similar to B cells, these provide long-lasting defense by mounting a faster attack if the same antigen is encountered again.1