Antigens are introduced in vaccines -- body produces antibodies and specialized lymphocytes

Artificially Acquired Active Immunity

1. inactivated bacterial toxins (toxoids)
2. killed microbes
3. Living but attenuated (weakened)
4. parts, such as capsules

Artificially Acquired Passive Immunity

A patient will need preformed antibodies in a life or death situation

• Anaphylaxis refers to the reaction when certain allergens combine with IgE antibodies
• Can be systemic (shock, difficulty breathing) or localized (hives, hay fever)
• IgE's bind to mast cells/basophils causing degranulation
• Mediators: histamines, prostaglandins, leukotrienes --> attract neutrophils and eosinophils

• Involves the activation of complement by the combination of IgG or IgM antibodies with an antigen
• Activation stimulates complement to lyse affected (foreign or host) cell that carries a foreign antigen

1. Transfusion reactions: ABO and Rh antigens
2. Drug induced reactions: in thrombocytopenia purpura, thrombocytes are destroyed by drug-induced cytotoxic reactions --> the drug molecules are known as haptens

• A drug molecule that enhances an immune response, causes an immune response
• Has to bind to carrier --> cannot initiate immune response on its own

In the example of Drug-Induced Thrombocytopenia Purpura:

1. Drug binds to platelet, forming hapten-platelet complex
2. Complex induces formation of antibodies against hapten
3. Action of antibodies and complement causes platelet destruction

• Involves antibodies against soluble antigens
• Immune complexes occur with certain ratios of antigen and antibody, usually IgG
• Too much antibody --> complement-fixing complexes are removed by phagocytosis
• Too much antigen --> soluble complexes form that do not fix complement and don't cause inflammation
• Slightly too much antigen --> soluble complexes can escape phagocytosis
• Common Outcome: Glomerulonephritis

• Caused mainly by T-cells
• Reactions not noticeable until a day or so after exposure due to T-cells and macrophage migration
• Antigens are phagocytosed and presented to receptors on T-cells (T-cell and Memory cell proliferation)
• Re-exposure causes memory cells to activate T-cells to release destructive cytokines

1. Skin test for tuberculosis
2. Allergic contact dermatitis (poison ivy, allergies to jewelery, cosmetics)