Lecture 10 Immune Cells & Inflammation

Two Components of the Immune System

Lymphoid tissue and immune cells

Primary Lymphoid Tissues

Thymus and bone marrow

Secondary Lymphoid Tissues

Encapsulated (lymph nodes and spleen) or unencapsulated (skin) diffuse lymphoid tissue.

Leukocyte

Another word for white blood cell

Six Types

Basophils/mast cells, eosinophils, neutrophils, monocytes/macrophages, dendritic cells, and lymphocytes/plasma cells

In Bone Marrow

Pluripotent stem cells, committed progenitor cells, megakaryocytes, and reticulocytes

In Circulation

Eosinophils, basophils, neutrophils, monocytes, platelets, and erthrocytes

In Tissue

Mast cells, dendritic cells, and macrophages

Basophils & Mast Cells

The two are related by mast cells are tissue resident. They release chemicals (cytokines) for inflammation and the innate immune response. Have dark blue granules in a stained blood smear.

Eosinophils

Defends against parasites and contributes to allergic reactions (releases enzymes to break things down). Bright pink granules when stained.

Neutrophils

Phagocytic cells, most abundant, has a segmented nucleus in 3-5 lobes. Made in the bone marrow, usually in circulation, but can extravasate. The amount present can be used to check for an infection.

Diapedesis

A cell’s ability to part two epithelial cells and crawl between them.

Extravasation

When neutrophils and monocytes leave the blood stream through diapedesis. The cells are attracted to the inflamed area by chemotaxis.

Phagocytosis

Cellular ingestion that breaks down the material with proteolytic enzymes. Rough surfaces (healthy cells are smooth and have a protective protein coat) make this easier.

Phagocytosis Waste

Disposed of, recycled, or displayed on immune cell surface for antibodies to target proteins that match.

Monocytes & Macrophages

Monocytes are macrophages’ precursor cells. They differentiate into M0 macrophages.

Macrophage System

M0 macrophage can be polarized to different macrophages on the M1-M2 spectrum.

M1 Macrophage

Causes fibrosis, promotes inflammatory response, reactive healing, “carpet bomb” the area to kill invaders w/some cell casualties.

M2 Macrophage

Releases different cytokines to promote regenerative healing and protect and promote cell viability.

Dendritic Cells

Links the innate and adaptive immune responses by eating bacteria and displaying parts of the bacteria on the surface. Has long thin extensions and is found in the skin as langerhans.

Lymphocytes

Primary effector cells for antigen-specific responses associated w/adaptive immunity.

Only Lymphocyte in Tissue

Plasma Cells

B & T Cell Specificity

Each binds only one particular antigen so millions are present in the body. If it’s been too long since seeing the foreign, you might have 1 for that invader until production is ramped up.

Plasma Cells

Makes antibodies

T Lymphocytes or T cells

Has T-cell receptors, has variety of types depending on if it’s part of adaptive or innate systems, and made in the thymus.

Adaptive T Cells

Helper, cytotoxic, memory, and regulatory.

Innate T Cells

Natural kill T cells, mucosal associated invariant, and gamma delta T cells

Thymus

Just above the heart, peaks in adolescence, and then turns into adipose tissue.