Immunology 2: Cells and organs of immune system

Hematopoiesis

Generation of blood cells

Hematopoietic stem cells (HSCs)

All blood cells derive from ___.

Bone marrow

Where do blood cells originate after birth?

Yolk sac, fetal liver/spleen

Where do blood cells originate before birth?

Neutrophils

Stain weakly with either acidic or basic dyes

3-5 lobes of nucleus

Most abundant immune cells in the blood

First responder at infection sites

Phagocytosis, degranulation

Functions of neutrophils

Abscess

Pocket of pus

Mixture of dead tissue, neutrophils, and pathogens

Anti-parasitic infection, allergic response

Functions of eosinophils and basophils

Eosinophil

Kills antibody-coated parasites through release of toxic granule contents

Basophil

Controls immune responses to parasites

Monocyte

Circulating precursor of macrophage

Macrophage

Phagocytoses and kills microorganisms

Mast cells

Release inflammatory mediators (histamine)

Contribute to innate defense against parasites and allergic reactions

Cytokines

Small, secreted proteins that serve as the immune system’s chemical messengers

Used by cells, particularly immune cells, to communicate with and regulate other cells

Cytokines

Macrophages are important producers of ___.

Dendritic cells

Irregularly branched, star-shaped

Located primarily in tissues

Functions:

Ag presentation to T cells

Cytokine production

Phagocytosis

Bursa of Fabricius

B-cells are named after this

Primary lymphoid organ in birds for B-cell development and Ab production

Plasma cells

Activated B-cells differentiate to become ___, which are major producers of antibodies.

Thymus

T-cells arise in the bone marrow and migrate to the ___ for maturation.

NK cells

Located in the blood and tissues

Cytotoxic molecules in the granule

Express both inhibitory and activating receptors

Kill virus-infected cells or tumor cells

Innate lymphoid cells (ILCs)

Located primarily in tissues

Main cytokine producer in innate immunity

No Ag receptor

Activated with cytokines produced by other immune cells

Bone marrow, thymus

Primary lymphoid organs

Sites of B and T lymphocyte development and maturation

Lymph nodes (LNs), spleen, MALT (mucosa-associated lymphoid tissue: adenoid, tonsil, Peyer’s patch, appendix, etc.)

Important secondary lymphoid organs

Sites where B- and T-lymphocytes are activated, responding to Ags