Pathopharm Immune Response

Granulocytes include neutrophils, eosinophils, and basophils. They contain granules and are primarily involved in the innate immune response.
- Neutrophils are the most common type, crucial for fighting bacterial infections quickly by engulfing and killing pathogens.
- Eosinophils combat parasites and play a role in allergic responses.
- Basophils release histamine and play a role in inflammatory responses, especially allergic reactions.
Agranulocytes include lymphocytes and monocytes. These cells do not contain granules and are key in both innate and adaptive immunity.
- Monocytes mature into macrophages and dendritic cells which phagocytize pathogens and present antigens, crucial for initiating adaptive immune responses.
- Lymphocytes include T cells, B cells, and natural killer cells. They are central to adaptive immunity, with specific responses and memory against pathogens.

MHC Class I proteins are found on all nucleated cells and present peptide fragments from within the cell to cytotoxic T cells. They are crucial when cells are infected internally by viruses or have become cancerous.
MHC Class II proteins are expressed on "professional antigen-presenting cells" (macrophages, dendritic cells, and B cells) and present antigens acquired from external sources to helper T cells.
Together, MHC I and II ensure that the immune system can monitor both intracellular and extracellular environments.

T-Cells:
- Helper T cells (CD4+) activate other immune cells by releasing cytokines.
- Cytotoxic T cells (CD8+) kill infected cells directly.
- Memory T cells provide a faster response upon re-exposure to the same pathogen.
- Regulatory T cells help maintain immune tolerance and prevent autoimmune diseases.
B-Cells mature into plasma cells that produce specific antibodies (immunoglobulins) against antigens. Memory B cells remain in the body to respond to future exposures.
Natural Killer Cells are part of innate immunity and kill cells that don’t properly present MHC molecules.

This system enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells, promote inflammation, and attack the pathogen’s cell membrane.
Chemotaxis attracts immune cells to the site of infection.
Opsonization marks pathogens for destruction by phagocytes.
Engulfment and intracellular killing are the mechanisms by which phagocytes consume and neutralize pathogens.
The Domino Effect in the complement system refers to a cascade of reactions that amplifies the response to destroy pathogens.

Antigens are substances that can induce an immune response; they include proteins on pathogens, mismatched blood cells in transfusions, and cells from other individuals in organ transplants.
Cytokines are signaling proteins released by cells that affect the behavior of other cells. Examples include interleukins, interferons, and tumor necrosis factors, which help in immune regulation and inflammatory responses.

The primary immune response occurs when an antigen is first encountered. B-cells produce antibodies and memory cells.
The secondary immune response is more rapid and robust due to the presence of memory cells.

Include IgG, IgM, IgA, IgE, and IgD, each with specific roles in immune defense, such as crossing placental barriers (IgG) or mediating allergic reactions (IgE).

Bone Marrow Cells: Produce blood cells, including immune cells.
Thymus Gland: Where T cells mature.
Lymph Nodes and Vessels: Filter pathogens and facilitate interaction between immune cells.
Spleen: Filters blood, traps blood-borne pathogens, and destroys old red blood cells.
Appendix and Tonsils: Part of lymphatic system, involved in monitoring ingested pathogens.

As we age, the immune system becomes less efficient; thymus size reduces, and immune responses become slower, increasing susceptibility to infections and diseases.

Active Immunity: Results from exposure to a disease-causing agent, leading to the production of memory cells.
Passive Immunity: Involves the transfer of antibodies from another source (e.g., maternal antibodies or immunoglobulin therapy).
Vaccines work by mimicking infection, stimulating the body’s adaptive immunity without causing illness, thus preparing the immune system for future real exposures.