B and T cells develop in bone marrow

B cells remain and mature in bone marrow

T cells mature in thymus

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[image]Adenoids and tonsils are key immune tissues

Lots of lymph nodes -- serve as filters for lymph fluid and drain most exterior surfaces of the body and filter out foreign objects

Thymus -- T cells mature here and are then released into circulation (as we age the thymus disappears and by age 40-50 the thymus is almost impossible to see)

Spleen -- plays a key role in filtering blood

Small intestine contains lymph nodes

Peyer's Patches -- play a role in immune response innitiation

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Cortex is primarily the T cell region

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Afferent lymphatic vessels = inflow of lymph fluid

Efferent lymphatic vessels =  outflow of lymph fluid

Follicle area = mostly B cells

Germinal Center = mostly B cells

Cortical area = mostly T cells

Medulary cords = mostly macrophages (to recognize free antigen in the lymph fluid)

Naïve and memory B and T cell present in the lymph nodes

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Blood in the central artery of the spleen passes first through a T cell zone and then through a B cell zone

Primary responsibility of the spleen it to filter the blood for foreign particles

Absolutely key to the antigen presentation

In the blood they are called monocytes

In the tissues they are called macrophages

In the brain they are called microglial cells

In the liver they are called Kupffer cells (produce complement proteins)

In the lungs they are called alveolar macrophages

In the joints they are called synovial A cells

All focused on phagocytizing foreign antigen, processing it and presenting it to T and B cells

Antigen presenting cells that stimulate T cells and initiate adaptive immunity

A key role in determining the type of immune response

Distinct DC subsets differ in cytokine profiles

CD8α⁺ DCs induce Th1 cytokines (IFN-γ and IL-2)

CD8α^- DCs induce Th2 cytokines (IL-4 and IL-10)

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After antigens are phagocytized, they are broken down in the phagolysosome and short peptide pieces are presented on the cell surface by a MHC protein.  If the antigen in non-self, then the antigen presentating cell will also express B7 on its surface.  T cells will not be activated unless B7 is expressed on the antigen presenting cell.

When the neutrophil takes oxygen and produces a very potent oxygen radical that can be an antimicrobial agent

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Mucky Baby/Clean Baby

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Mucky Baby = greater TH1 response; greater cell mediated response

Clean Baby = greater TH2 response; greater antibody mediated response

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Clean Adult has more allergies (type I hypersensitivity)