• Humoral Immunity
• Cellular Immunity

• B-Lymphocytes(Activated B-Cells)→Plasma Cells
• Plasma cells secrete immunoglobins (Ig's) into tissue fluids. (humors)
• Battle from far away

• T-Lymphocytes(Activated T-Cells) directly contact and kill the invading cell.
• Hand to hand combat

• They look like two "h" placed back to back.
• The top of the "h" is the cell binding(Fc) region. This is where it would bind to other immunoglobins. Contains Carboxyl group.
• Heavy Chain: backbone of the "h". Twice as big as the light chain.
• Light Chain: small arm of the "h".
• Variable Region: near the very bottom of the "h". Antigen specific. Both chains have them. Also is Antigen Binding Region(Fab)
• Constant Region: The rest of the "h". Identical in all immunoglobins. Both chains have them.
• Di-Sulfide bonds: connects the backbones of the two "h's" together. Also connect the small arm of the "h" to the backbone.

• Most abundant serum Ig.
• Major Ig in secondary response
• Greater antigen specificity
• Usually a monomer

• 2nd most aboundant in serum.
• found on surface of virgin B-Lymphocyte(before its activated to Plasma cell)
• When activated the usually form pentamers.
• Major in Primary Response.
• Less antigen specific

• Secretory Ig (eg. mucus, saliva, tears, milk)
• Rare in serum
• Two IgA's linked together by a J-Chain. (cell binding region of course)(dimer)
• Secretory piece/ transport component (protein) is contributed by lining epithelial cells and allows the IgA to be transported from epethelial cell's basal surface to the lumen to be secreted.

• Allergic Ig
• Binds to Fc(Cell Binding Region) receptors on Mast Cells and Basophils.
• When antigens(allergens) bind to IgE (actually forms a cross-bridge by binding two IgE's) it stimulates the release of Histamine.

• Neutralization
• Opsonization
• Complement Activation

• Immunoglobins surround foreign cell and try to occupy all of it's antigen sites.
• May inactivate it
• Subsequently undergoes phagocytosis by macrophages, neutrophils, or easinophils.

• Foreign cells that have immunoglobins(antibodies) attached to them are marked for phagocytosis.
• Eosinophils, macrophages, cytotoxic T cells, and neutrophils to the phagocytoses
• The antibodies (IgM,IgG) act as opsonins.

• Antibodies(IgM, IgG) activate enzymes that drill holes in and kills foreign cell.

IgD

Often seen on the surface of B-Lymphocytes with IgM

• Lymphocytes
• Macrophages
• Plasma Cells
• Reticular Cells
• Other Antigen-presenting Cells (Dentritic, Langerhans, Kupferr cells)

1. B and T cells precursors are produced in bone marrow.
2. T cells migrate to the Thymus where they are programmed as Helper(CD4+) or Cytotoxin(CD8+).
3. They reenter circulation and mature (programmed to respond to certain antigen) in secondary lymphoid organs.(spleen or lymph nodes)

Memory T cells can last for years.

• B and T cell precursors are produced in bone marrow.
• They are programmed to be B cells in the bone marrow.
• Go to secondary lymphoid organs(spleen, lymph nodes) to be programmed for certain antigen.
• If it encounters antigen it undergoes blast transformation and clonal expansion.
• The expansion results in effector cells(Plasma) and Memory cells

§  Carry CD8 antigen on surface

§  Activated by antigen complexed with major histocompatability complex class I (MHC-I) molecules

§  Carry CD4 antigen on surface

§  Activated by antigen complexed with major histocompatability complex class II (MHC-II) molecules

§  Proteins in coat of HIV bind selectively to CD4

§  Highly branched structure

§  Exact origin unknown (except that they are mesenchymal)

§  Present antigen on their surface without phagocytosing it.

§  Much longer lived than macrophages, thus assist with immunologic memory

Hold AIDS on the surface

lymphoid system Stroma

Reticular Connective Tissue

• Nodules and Aggregates
• occur especially at branch points where two or more organs join where there is transitional epithelial lining.
• classic example is Peyer's patches, nodules of the small intestine.
• Lamina Propia of Hollow Organs. Digestive, Urinary, Respitory, Reproductive systems

Primary: has Mantle Zone which is made up of small Lymphocyte memory cells. Dark color.

Secondary: has mantle zone around a Gremline Center which has light colored Lymphoblasts. This is a response to an antigen.

Primary(Central): Bone Marrow and Thymus. Lymphocytes divide withOUT antigen stimulation.

Secondary(Peripheral): Lymph nodes, Spleen, Tonsils. Lymphocytes need antigen stimulation to divide.

• Located in Mediastinum, behind heart.
• Bigger in smaller children.
• T-Lymphocyte programming
• Primary (Central) Lymphoid Organ

• Densely packed with thymic lymphocytes (thymocytes)not programmed
• Surround Medulla
• Stroma: Reticular cells but no reticular fibers. Cytokeritin
• Blood thymus barrier(capillaries only): prevents antigens from getting in and pre-programmin thymocytes.
• Antigen-Independent thymocyte proliferation
• T-cell programming.

• Loose cell packing
• more reticular cells than lymphocytes.
• Mature T cells enter circulation
• Stroma: reticular cells, dendritic(Langerhans) cells, macrophages, fibroblasts.
• Hassal's corpuscles.

• Derived from endoderm
• Produce thymic hormones & cytokines
• Contribute to blood-thymus barrier
• Joined to each other at their tips by desmosomes

• In time your cortex and medulla get replaced by fat.
• Hassal's corpuscles enlargs and my calcify.