Immune System I

Immune system

All tissues, cells, secreted molecules, and messengers are involved in sensing “self” from “non-self”

Is the immune system restricted by tissue types

immune system is not restricted by tissue types; it is broadly found throughout the body and/or migrating through blood, lymph, and lymphoid organs

Goals of immune system

1. protection against infection from pathogens

2. isolate and eliminate pathogens

3. destroy cancer cells

Immunology

Study of how the body defends itself against infection from different microorganisms

Leukocyte definition

White blood cells originating from the hematopoietic stem cell (HSC) of the bone marrow (BM).

Leukocyte purpose

Carry out cellular effects of the immune response and contribute to the chemical effects of the immune response

Primary (Generative) Lymphoid Tissues

Bone Marrow and Thymus are primary lymphoid organs, which generate all circulating leukocytes

Secondary Lymphoid Tissues

Secondary lymphoid tissues include the lymph nodes, spleen, tonsil, GI tract, respiratory tract, and urogenital tract and are the primary sites for generation of adaptive immune responses

Ectopic/tertiary lymphoid tissues

can develop at sites of strong immune response

Pathogens

infectious organisms: Bacteria, Viruses, Parasites, Fungi, Helminths, and Prions

Pathogen-Associated Molecular Patterns (PAMPs)

molecular structures commonly found on pathogens that distinguish foreign invaders from host cells

Pattern Recognition Receptors (PRRs)

recognize Pathogen-Associated Molecular Patterns (PAMPs)

Toll-Like Receptors (TLRs)

activated by many different pathogens like bacteria, viruses, fungi

NOD-Like Receptors (NLRs)

bind bacterial peptides

RIG-Like Receptors (RLRs)

recognize viruses

C-type Lectin Receptors (CLRs)

recognize fungi. Subtypes include macrophage mannose receptor (MR) and dendritic cell-associated C-type lectin (Dectin)

Antigen

Any molecule that can stimulate an immune response; a molecule can bind to an antibody or another molecule can generate peptide fragments that are recognized by a T-cell receptor.

Immune Surveillance

the recognition of cancer cells and in some cases elimination of cancerous cells

Immune Tolerance

the failure to respond to an antigen. Tolerance to self-antigens is an essential feature of the immune system

Antibody (Immunoglobulin; Ig)

Membrane-bound or secreted molecule with characteristic Ig folds, Variable region, and Constant region

Antibody characteristics

Multiple isotypes (classes) carry out diverse functions. Antibodies can exist as monomer, dimer, or pentamer

Neutrophil (NΦ)

among first cells in innate response (antimicrobial, phagocytosis)

Eosinophil

defense against parasite

Basophil

key role in parasite response and allergy response

Mast Cell

release histamine; involved in stimulation of innate immunity and inflammation

Dendritic Cell (DC)

phagocytosis of pathogen for destruction and presentation to T-cells

Monocyte

circulate in blood and transform into macrophage when entering tissues

Macrophage (MΦ)

role in phagocytosis, secretion of cytokines during innate response

T-cell

mediate cellular arm of adaptive immunity

B-cell

mediate humoral arm of adaptive immunity

Natural Killer cell (NK)

mediate innate defense; killing cancer cells and virus-infected cells

Plasma Cells

differentiate from B cells during immune responses; secretion of immunoglobulins

Myeloid lineage

cells that differentiate from common myeloid progenitor

Myeloid lineage cell types

dendritic cell, neutrophils, eosinophils, basophils, monocytes which leave BM through blood into tissue and become macrophages, mast cells, RBCs, megakaryocytes, and platelets

Lymphoid lineage

cells that differentiate from common lymphoid progenitor

Lymphoid lineage cell types

Dendritic cells, natural killer cells, B cells, T Cells