Module 3: Cells and Lymphoid Organs of the Immune System

Hematopoietic stem cells (HSC)

Myeloid progenitor cells (MPC) and lymphoid progenitor cells (LPC)

HSCs differentiate into what 2 separate lineages

Red blood cells, platelets, neutrophils, monocytes, eosinophils, basophils, mast cells, and certain dendritic cells

Myeloid progenitor cells (MPC) further differentiate into

T and B lymphocytes and specific dencritic cells

Lymphoid progenitor cells (LPC) further differentiate into

Types of dendritic cells

Both MPCs and LPCs give rise to

Steady state level

A homeostatic condition thay is maintained under normal conditions (without infection or immune challenges) It is the number of cells that arise from division and differentiation and the number of cells removed by apoptosis

• Levels and types of cytokines produced by bone marrow stromal cells

• Cytokines produced by activated cells

• Regulation of receptor expression by stem and progenitor cells

• Apoptosis

Steady state is regulated by (x4)

3.7×10^11

Human body produces approximately how many white blood cells a day

Membrane-bound immunoglobulins (mIg)

B-lymphocytes possess

T-helper cells and cytotoxic-T cells

T-cells are divided into

CD4+

T-helper cells have what CD marker

CD8+

Cytotoxic T-cells have what CD marker

Natural killer cells (NK)

Lymphocytes part of the innate immune response that can kill host cells (e.g. virus infected cells) without making their own antigen-specific receptors (thus they lack T-cell receptors and mIg)

NKs and cytotoxic T-cells

What cells contain cytoplasmic granules with lytic enzymes

Lytic enzymes

Enzymes that kill virus-infected cells upon contact

Cancer and viral infection

Low NK cell count means an individual is more prone to

Cluster of differentiation markers (CD markers)

Specific type of molecules found on the surface of cells that help differentiate one immune cell type from another and also function in cell signaling and adhesion

Monocytes

Migrate to tissues and differentiate into various macrophages

Differentiated macrophages

Larger macrophages perform specific functions based on their location and have different receptors based on their tissue-specific location (contain more hydrolase enzymes, have increased phagocytic ability, and contain a variety of soluble factors)

Professional antigen-presenting cells (pAPC)

Regardless of differentiation all macrophages act as

Microglia

Brain tissue macrophages that function in neural circuit development (synaptic pruning)

Alveolar macrophage

Lung tissue macrophages that function to remove pollutants and microbes and clear surfactants

Kupffer cell

Liver tissue macrophages that function to scavenge RBCs and clear particles

Resident kidney macrophage

Kidney macrophages that function to regulate inflammatory responses to antigens filtered from blood

Langerhans cell

Skin macrophages that function in skin immunity and tolerance

Red-pulp macrophage

Spleen macrophage that function to scavenge RBCs and recycle iron

Peritoneal cavity macrophage

Peritoneal cavity macrophages that function to maintain IgA production by B1 B-cells

Lamina propria macrophage and intestinal muscularis macrophage

Intestinal macrophages that function to regulate peristalsis in gut immunity and tolerance

Bone marrow macrophage

Bone marrow macrophages that function to maintain niche for blood cell development and clear neutrophils

Subcapsular sinus macrophage

Lymph node macrophage that function to trap antigen particles

Cardiac macrophage

Heart macrophages that function to clear dying heart cells

Phagocytes ingest exogenous antigens

Macrophages are activated when

Opsonization

Process by which particulate antigens or microbes are rendered succeptable to phagocytosis

Opsonization process explained

Macrophages have receptors for antibodies (Fc receptor) and complement (CR1), then antigen coated with antibody binds to macrophages via recognition by specific T-helper cells and then the antigen undergoes phagocytosis; Makes it easier for macrophage to capture and antigen because of the receptor

Opsonin

Molecule (either antibody or complement component C3b) that binds to antigens and macrophages thereby enhancing phagocytosis

Complement components (like C3b) and antibodies bind to microbes marking them for destruction

Enhanced phagocytosis occurs when

Neutrophils

First responders at inflammation site (make up 50-70% of circulating leukocytes) that function to kill microorganism

Hypochlorous acid that acts as an oxidizing agent

Neutrophils are the only type of cell that produce what to kill organisms?

Neutrophil structure

Multilobed nuclei that contain granules with microbial a

Neutrophilia

Infection that causes

Eosinophils

Play a crucial role in defending against