Immune Organs - organs of the immune system And immune cells.

1. TISSUES OF THE IMMUNE SYSTEM
The tissues of the immune system consist of the generative lymphoid organs, in which T and B lymphocytes
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mature.
Mature T cells; activated T cells proliferate + migrate to sites of inflammation to eliminate infection.
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Mature B cells; activated b cells gives rise to plasma cells and memory cells.
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Organs of the immune system
A) primary lymphoid organs
thymus (develop mature T cells)
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bone marrow (develop mature B cells)
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fetal liver (hematopoiesis - making blood cells)
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B) secondary lymphoid organs (site of immune activation):
spleen
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lymph nodes
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mucosal-associated lymphoid tussle (MALT)
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1) Lymph Nodes;
This gland works in conjunction with the spleen; acts as a filter for the lymph, a place where white blood cells
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fight infection.
Bean-shaped filters that cluster along the lymphatic vessels of the body.
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They function as a cleanser of lymph as wells as a site of T and B cell activation.
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2) Thymus;
Produces white blood cells that destroy germs. (T-cells)
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An immune organ located near the heart. This is the site of T cell maturation and is larger in children and
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adolescents.
3) Spleen:
Works in conjunction with the lymph nodes; recycles red blood cells; a place where white blood cells fight
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infection.
An organ that is part of the lymphatic system; it produces lymphocytes, filters the blood, stores blood cells, and
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destroys old blood cells.
4) Appendix:
A safe house for beneficial bacteria, protects rather than harms, good bacteria needed for digestion.
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A small, fingerlike extension of the vertebrate cecum; contains a mass of white blood cells that contribute to
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immunity.
5) Bone Marrow;
Develops stem cells that mature into white blood cells (B-Cells) that fights infection and destroys germs.
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A soft tissue inside the bone that produces blood and immune cells.
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6) Tonsils;
help protect from infection by trapping germs coming in through your mouth and nose and destroy germs in
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your throat.
A ring of lymphoid tissue around the entrance to the pharynx.
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7) Adenoids;
help protect from infection by trapping germs coming in through your mouth and nose and destroy germs in
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your throat.

2. Lymphoid tissue located behind the nasal cavity.
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8) Lymphatic Vessels;
A system of vessels that carries lymph through the body into the nodes; different from blood vessels; lymph
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drains tissues and contains white blood cells that fight against germs.
Located deeper within the tissues that has lymph flowing to them from the lymphatic capillaries.
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9) Peyer's Patches;
Macrophages captures and destroys bacteria, prevents them from penetrating through intestinal walls.
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10) Skin;
The first line of defense; if not unbroken cannot be pierced by most microbes.
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4 Types of Immune Cells
1) Leukocytes; White Blood Cells.
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2) Plasma Cells; Make and secrete antibodies.
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3) Macrophages; Engulf invading particles
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4) Mast Cells; Trigger inflammatory response
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Principal cells of the immune system (4 types of Lymphocytes;)
1) B Cells; Recognize foreign antigens: secrete antibodies to guide attack.
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2) Cytotoxic T Cells; Recognize and attack cancerous and infected cells.
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3) Helper T Cells; Help Activate B Cells and Cytotoxic T Cells: Are attack by HIV. Type of Lymphocyte.
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4) NK Cells; Kill Cells with guidance from antibodies.
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Naive and effector lymphocytes and Memory cells
1) Naive cells; are mature T or B cells that have not been activated by an microbe antigen yet.
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They pass through the circulation in lymph nodes or wait in the tissue for a breach.
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Naive T lymphocytes flow through the peripheral organs and recirculate until activated by an antigen.
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2) Effector cells; are activated in the lymph node but go to the site of infection where the antigen may be
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located.
have been activated in some way by the presence of a pathogen. These cells elicit an antimicrobial defense to
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protect or eliminate pathogens. Most effector cells die after some time, but some live on.
3) Memory B cells; live on after the immune response dies down. They can change isotopes of antibody
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immunoglobulin to improve affinity and specialize for particular antigens. Improve reaction to second exposure.
T cells
recognize, ingest and destroy microbes, display their peptides to B cells activating their humoral response
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Types of T cells
1) Cytotoxic T Cells( CD8 cells); Destroys host cells that harbour anything foreign. They are directly
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responsible for cell mediated immunity.
2) Regulatory cells; inhibit multiplication of cytokine secretion by other t cells *limit immune response.
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3) Supressor T Cells; Turn off an immune response.
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4) Memory T Cells; Jump start an immune response to an antigen that was previously present in the body.
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They remain in the body.
5) Helper T Cells(CD4 cells); Modulate activities of OTHER immune cells.
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helps promote t cell and b cell action and non specific resistance.
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3. The major role of Th1 cells is to secrete IFNɣ and A major activity of IFNɣ is to activate.
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Th1;
response is characterized by the production of interferon - gamma.
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secrete IL-2, IL-12, IFN gamma, TNF-beta;
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produce IFNγ and promote cellular immunity
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activate macrophages, amplifying their cytokine secretion capacity and potential for
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presentation of antigens;
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activate synthesis of IgG but not IgE;
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are involved in delayed hypersensitivity reactions;
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are activated by signals from intracellular bacteria and viruses;
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Th2
secrete IL-4, IL-5, IL-6, IL-10;
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activate the synthesis of IgE;
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stimulate proliferation and activation of eosinophils;
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are stimulated by allergens or parasite components.
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Th2 response is characterized by the release of interleukin 4
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Th2 produce IL-4 and promote humoral immunity
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B cells
B cells - secrete antibodies that bind to antigens, or initiate the complement system,
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Differentiate into plasma cells and produce antibodies.
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are formed in the bone marrow.
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are located in the germinal centers of lymph nodes, white pulp of the spleen, and GALT.
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B-cell activation occurs in the secondary lymphoid organs such as the spleen and lymph nodes.
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Six Types of B-Cells; Plasmablast, Plasma Cell, Memory B-Cell, Follicular B-Cell, Marginal Zone B-Cell and
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Regulatory B (Breg) Cell.
are five types of antibody IgA, IgD, IgE, IgG, and IgM,
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IgM; is the basic antibody produced by B-cells.
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B lymphocytes;
B lymphocytes are the only cells capable of producing antibodies
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B-lymphocytes function in the humoral immunity component of the adaptive immune system by secreting
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antibodies.