Immune System

  • Barrier defenses and roles 

  • Skin, mucus and sweat, stomach acid, and lysozymes in tears (not fever) 

  • Adaptive vs innate immunity 

  • Adaptive – specific to a foreign invader. Requires previous infection with that invader 

  • Innate – non-specific response 

  • Phagocytosis  

  • Natural Killer cell activity 

  • Non-specific lymphocytes 

  • Trigger apoptosis 

  • Can release perforins and granzymes to destroy cells 

  • Process of inflammation 

  • Foreign invader enters 

  • Triggers mast cells and basophils to release cytokines (mobilize WBC’s) and histamines (inc blood flow to areas via leaky and dilation) 

  • Leukocytes arrive and destroy invader 

  • Don't need to know that eosinophils digest histamines 

  • Roles of a fever 

  • Systemic inc in temp 

  • Inhibiting enzymes in bacterial cells and viruses, activate native immune cells 

  • Dec ATP production and oxygen distribution (dec cell respiration) 

  • Roles of MHC molecules 

  • Class I vs class II MHC 

  • 1 are widespread and most common. Find antigen and present to cytotoxic or NK 

  • 2 – only on APC’s that present antigen to learn their ID (macrophages, dendritic cells, and B cells). Dendritic cells live in lymph nodes. 

  • Activation by Class I MHC molecules 

  • All cells have MHC class 1 molecules 

  • Cytotoxic T cells bind MHC1 

  • T cell receptors bind tightly to a foreign antigen 

  • Aided by CD8 glycoprotein that act as co receptor 

  • Binding stimulates the T cell to activate apoptosis of infected cells by secretory granzymes and perforins 

  • Activation by Class II MHC molecules 

  • Only found in specialized phagocytic cells 

  • APC’s (dendritic cells, B cells, macrophages) 

  • Transport antigens to cell surface using MHC proteins 

  • Helper T cell (CD4) recognize new antigen as foreign 

  • Types of helper T cells and roles 

  • Type 1 

  • Activate macrophages and other T cells 

  • Destroy and eliminate pathogens 

  • Some remain as memory cytotoxic and helper T cells  

  • Create an immediate response if infection occurs again 

  • In some cases, memory T cells last throughout life 

  • Type 2 

  • Activate B cells 

  • B cell receptors modify to recognize antigen 

  • Triggers clonal expansion of the specialized B cells 

  • A few become memory B cells for future defense 

  • Most become plasma cells which actively produce antibodies and then die 

  • Plasma cell job = make antibodies 

  • Clonal expansion of B cells and plasma cells 

  • Makes copies of itself (most as memory cells) 

  • Clonal expansion = mitosis 

  • Antibody actions and pathways 

  • Bind to antigens to trigger 4 responses: 

  • Neutralization- binds to virus and prevents it from infecting cells 

  • Opsonization – binds to cell and targets it for destruction via macrophage 

  • Complementation – binds to cell and attracts complement proteins that cause apoptosis. Perforins perforate cell and granzymes go in and destroy? 

  • Agglutination – antibodies bind to multiple cells at once causing them to clump 

  • Primary vs secondary immune response 

  • Primary  

  • Can take several days 

  • 1st exposure 

  • Secondary  

  • Very rapid 

  • Not 1st exposure