I. Intro to Adaptive Immunity

Introduction

• Specific immune response to each pathogen 

• Several days  to mobilize 

Lymphocytes

• B Cells

• T Cells

• B Cells

• Originate from marrow

• Mature in Bone marrow

• Function: Create antibodies

• Defend against: Pathogens in blood

• T Cells

• Originate from bone marrow

• Mature in Thymus

• Function: attack infected cells

• Defends against: pathogens inside cells

Antigen (Ag):

• any foreign substance that elicits B or T cell response

  • Mostly proteins or polysaccharides on foreign organisms 

Epitope

• specific region exposed on surface of Ag 

  • Specifically binds Ag receptor of B or T cell

1. Self tolerance

• Depends on ability to distinguish self from non self

• Possible b/c individuals biochemically unique 

2. B and T cell diversity

• >10⁶ different B cell Ag receptors

• >10⁷ different T cell Ag receptors

• Generated via genetic recombination and deletion when cells activated

• Presence of receptors is what makes adaptive immunity specific 

3. Proliferation of B and T cells

• Once activated, multiple cell divisions -> many identical cells

• Can become…

• Effector cells: short lived, work immediately against Ag, any pathogen producing Ag

  • Plasma cells, helper T cells, cytotoxic T cells 

• Memory Cells: long lived, ready to divide if Ag, reappears

• Clonal Selection

• Cell proliferation based on use

• Mitosis -> direct clones

4. Immunological Memory

• Long term protection, result of prior infection

• Primary immune response: response to 1st exposure to Ag 

• Second immune response: response to subsequent exposure to same Ag

  • Faster, stronger, longer, lasting