Immunity Types

Immunity

• Natural active immunity occurs when an individual recovers from an infection, such as chickenpox.
• Artificial passive immunity involves the administration of antibodies from an immune individual.

Acquired Immunity

• Acquired immunity is characterized by specificity and memory.
• It involves a specific immune response mounted by the immune system against a particular pathogen.
• Memory B cells and T cells are primarily involved in the secondary immune response.

Cell-Mediated Immunity

• CD8+ T cells recognize peptides presented by MHC I class molecules.
• Regulatory T cells (Treg) limit or prevent immune responses.
• Naive lymphocytes are functionally inactive but able to recognize antigens.

Antigen Presentation

• Professional antigen-presenting cells (APCs) include dendritic cells, macrophages, and B lymphocytes.
• Lymph nodes concentrate antigens, APCs, and lymphocytes, facilitating the immune response.

Innate Immunity

• The innate immune system initiates a non-specific and rapid immune response.
• Toll-like receptor 4 (TLR4) is important for the recognition of microbial lipopolysaccharides (LPS).
• M1 macrophages initiate pro-inflammatory responses.

Cytokines

• IL-12 is primarily involved in the differentiation of naive T cells into Th1 cells.

Leukocyte Trafficking

• Selectins facilitate the initial weak binding and rolling of neutrophils on endothelial surfaces.

Immune Response

• Nitric oxide (NO) contributes to microbial destruction within phagosomes.
• Opsonins include IgG and C3b, which facilitate phagocytosis.