The cell-mediated innate immune system, which defends the host against pathogens, includes various cells. NK cells eliminate infected or abnormal cells, while macrophages and neutrophils engulf pathogens. Dendritic cells present antigens to T cells, initiating adaptive immune responses. Gamma-delta T cells provide quick immunity, and granulocytes detect and combat pathogens. Innate lymphoid cells, lacking antigen-specific receptors, contribute to early immune response.

The humoral innate immune system consists of naturally occurring antibodies, pentraxins, the complement system, and the contact system. These components defend the body from various pathogens. Naturally occurring antibodies and pentraxins recognize and neutralize pathogens. The complement system enhances immune responses, while the contact system aids in immune cell recruitment and pathogen clearance.

The immune system employs two distinct strategies to defend against pathogens: humoral and cell-mediated immunity. Humoral immunity, mediated by B lymphocytes and antibodies, is effective against extracellular threats like bacteria and viruses in bodily fluids. Cell-mediated immunity, involving T lymphocytes, targets intracellular pathogens and cancerous cells, providing comprehensive defense.