barriers (skin, pH, enzymes)

innate immune system (neutrophils)

adaptive immune system (B, T cells)

• molecules, cells that distinguish host cells from infectious agents
• mechanism of action
  • recognizing limited number of conserved constituents of microbes (use germline encoded pattern recognition receptors)
  • activated within hours of exposure
  • efficacy/activity not significantly changed by previous exposure

• immune responses mediated by lymphocytes
• recognize unlimited number of antigens
• efficacy of response not seen until 2-4 days after exposure
• increased efficiency of response upon subsequent exposure

neutrophils

eosinophils

macrophages

dendritic cells

bone marrow

thymus

lymph nodes

spleens

MALT

What distinguishes primary lymphoid organs from secondary?

primary- site of development

secondary- residence

• generally, along with spleen, primary spot of immune reactions 
  • filter lymph
  • concentrate antigens

• B cells- primary lymphoid follicle, in the cortical region
• T cells- paracortical region

Blood lymphocytes leave the blood and enter the lymph node via what vessel?

1. bacteria triggers macrophage to release cytokines and chemokines that causes vasodilation
2. vasodilation and increased vascular permeability (fluid leaks between blood stream and tissue space) causes redness, heat, swelling
3. inflammatory cells migrate into tissue, releasing inflammatory mediators that cause pain

1. immature dendritic cells resides in peripheral tissue, and mature upon recognition/binding to the pathogen
2. dendritic cells migate via lymphatic vessels to regional lymph nodes
3. mature dendritic cells activate naive T cells in lymphoid organs such as lymph nodes

native antigen

Describe process of clonal selection theory

1. clones/lymphocytes exist even before antigen exposure
2. specificity exists prior to antigen exposure
3. antigen select lymphocyte with best fit
4. activated lymphocytes expand (clonal expansion)
5. self reactive lymphocytes are deleted as they mature (avoid autoimmunity)
6. clones that react with self are eliminated during development

How is the diversity of our immune system receptors generated?