Principles and Mechanisms of Immunity

Cell-Mediated and Humoral Immune Responses

The immune system plays a vital role in defending against pathogens and maintaining homeostasis. It comprises two primary branches: the cell-mediatedhumoral

Cell-Mediated Immunity

Cell-mediated immunity (CMI) involves the activation of T lymphocytes that target infected or abnormal cells.

• Helper T cells (CD4+): Enhance the immune response by releasing cytokines.
• Cytotoxic T cells (CD8+): Destroy infected host cells.
• Regulatory T cells: Modulate immune responses to prevent excessive inflammation.

Humoral Immunity

Humoral immunity primarily involves B cells and the production of antibodies to neutralize extracellular pathogens.

• B lymphocytes: Differentiate into plasma cells that secrete antibodies.
• Immunoglobulins (IgG, IgA, IgM, IgE, IgD): Mediate various immune functions.
• Memory B cells: Provide long-term immunity upon re-exposure to antigens.

Mechanisms of Immune Activation

Both CMI and humoral responses involve antigen recognition, activation of immune cells, and effector functions to eliminate pathogens.

Clinical Implications

Dysfunctions in immune responses contribute to conditions like autoimmune diseases, immunodeficiencies, and hypersensitivity reactions.

Conclusion

Understanding the principles of immunity enhances disease management and therapeutic interventions in microbiology and medicine.