Body Compartments in Immune System

Body Compartments that Participate in the Immune System

• The bloodstream, mononuclear phagocyte system, and lymphatic system are the three body compartments that participate in the immune system.

Hematopoiesis

• Hematopoiesis is the production of blood cells.
• All blood cells arise from Hematopoietic Stem Cells (HSC).
• HSCs are the 'mother' of all blood cells and can self-renew.
• HSCs can differentiate into two main types of cells: myeloid and lymphoid progenitors.
• Myeloid progenitors can differentiate into granulocytes, macrophages, monocytes, erythrocytes, megakaryocytes, eosinophils, and basophils.
• Lymphoid progenitors can differentiate into lymphocytes and natural killer (NK) cells.

Hematopoietic Homeostasis

• Erythrocytes have an average life span of 120 days and are phagocytosed by macrophages in the spleen.
• White Blood Cells (WBCs) have a life span of 1 day to 20-30 years.
• Apoptosis is a programmed cell death that contributes to hematopoietic homeostasis.

Mononuclear Phagocyte System

• The mononuclear phagocyte system is a network of connective tissue fibers and cells surrounding organs.
• It is inhabited by phagocytic cells that are ready to attack and ingest microbes that have passed the first line of defense.

Lymphatic System

• The lymphatic system provides an auxiliary route for the return of extracellular fluid to the circulatory system.
• It acts as a drain-off system for the inflammatory response.
• It renders surveillance, recognition, and protection against foreign material.

Lymphoid Tissues and Organs

• Lymphoid tissues and organs can be classified into primary and secondary lymphoid organs.
• Primary lymphoid organs are responsible for the development and maturation of lymphocytes, whereas secondary lymphoid organs are responsible for the activation of mature lymphocytes.

Primary Lymphoid Organs

• The thymus is a primary lymphoid organ responsible for T cell development and maturation.
• It induces the death of T cells that cannot recognize self-MHC molecules or interact with MHC molecules too strongly.

Secondary Lymphoid Organs

• Secondary lymphoid organs include spleen, lymph nodes, tonsils, appendix, and mucosa-associated lymphoid tissue (MALT).
• Lymph nodes are responsible for filtering lymph, activating lymphocytes, and producing plasma cells and antibodies.
• The spleen is a lymphoid organ in the upper left abdomen that filters blood, activates lymphocytes, and produces plasma cells and antibodies.
• MALT is a organized area along the digestive, respiratory, and urogenital tracts that is responsible for immune response to pathogens.

Host and Antigen Factors in Immunogenicity

• Host factors that influence immunogenicity include genotype, dosage, and administration of the antigen.
• Antigen factors that influence immunogenicity include foreignness, molecular size, chemical composition, and the presence of adjuvants.

Innate vs. Adaptive Immunity

• Innate immunity is non-specific, pre-existing, and responsive to a wide range of pathogens.
• Adaptive immunity is specific, responsive, and acquired through exposure to pathogens.

This quiz covers the different body compartments that participate in the immune system, including the bloodstream, mononuclear phagocyte system, and lymphatic system. Understand the role of each compartment in acquired immunity.