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USMLE
Immuno - Complement/IFNs
| Question | Answer |
|---|---|
| Type I MHC is on what cells | All nucleated cells (this excludes adult RBCs) |
| Type II MHC is on what cells | Antigen presenting cells |
| Name the antigen presenting cells | Macrophages Dendritic cells Langerhans cells B cells |
| Which MHC specific for viruses | Type I |
| Which MHC specific for bacteria | Type II (Antigen presenting cells) |
| Characteristics of innate immunity | Nonspecific Rapid Physical barriers Phagocytosis Complement Interferons Lysozymes Induces fever, inflammation |
| Characteristics of acquired immunity | Specific Slow, then rapid Inducible Memory Antibodies B and T cells |
| Alpha & Beta interferons are produced by? | Alpha: leukocytes Beta: fibroblasts |
| How do interferons inhibit viral replication | place uninfected cells in "antiviral state". Alpha & beta induce a 2nd protein which degrades viral (but not host) mRNA thereby inhibiting viral protein synthesis |
| Steps to "interfere" with viruses | 1) alpha & beta interferons inhibit viral protein synth 2) gamma-interferons incr. MHC I and II expression & antigen presentation in all cells 3) Activate NK cells to kill virus-infected cells |
| Describe neutrophils | Formed in bone marrow Multi lobed nucleus Granules Early defense against bacterial infxn |
| Which cells are increased in pyogenic infections | Neutrophils |
| Macrophages develop in ___ as ___ | bone marrow monocytes |
| Role of Basophils | Release of pharmacologically active substances contained within granules - Allergies |
| Role of Eosinophils | Major role against parasites - Secretion of eosinophilic granules results in damage to parasite membrane. Also involved in asthma & allergy |
| NK cells target what cells | those with decreased MHC class I expression |
| NK cells have 2 types of receptors - what are they | Inhibitory - recognizes MHC alpha chains Stimulatory - recognizes cell signals |
| The 3 complement pathways are components of which immunities? | Classical: Aquired Alternative: Innate Lectin: Innate |
| When all 3 complement pathways converge, they create __ ? | MAC - (membrane attack complex) |
| Define: complement | System of proteins that interact to play a role in humoral immunity & inflammation |
| What are the functions of the complement cascade? | 1. Lysis of cells, bacteria, viruses 2. Opsonization to promote phagocytosis of Ag 3. Activation of inflammatory response 4. Clearance of immune complexes |
| Describe the classical pathway complement cascade. | 1. C1 cleaves C4 into C4a and C4b 2. C1 cleaves C2 into C2a and C2b 3. C4b binds to pathogen surface 4. C4b binds C2a 5. C4bC2a cleaves C3 into C3a and C3b 6. C3b binds to pathogen surface 7. C3b cleaves C5 into C5a and C5b 8. C5b activates |
| Describe the alternative pathway complement cascade. | 1. C3b binds to bacterial cell 2. C3a promotes inflammation, C3b promotes opsonization 3. C5-C9 promotes cell lysis |
| Factors B, D and properdin are ONLY a part of which complement pathway? | alternative (properdin is important for stability of pathway) |
| Describe the lectin pathway? | 1. Activated by binding of mannose-binding lectin, an acute phase protein found on the surface of microorganisms. 2. MBL cleaves C4 and C2 3. activates complement (C5-C9) |
| MAC defends against what via lysis? | Gram(-) bacteria and viruses |
| Why are gram(+) essentially safe from MAC? | gram(+) bacteria have thick PG coats and MAC has trouble creating pores in it |
| How is MAC activated via the CLASSIC pathway? | IgG or IgM ("GM makes classic cars") |
| How is MAC activated via the ALTERNATE pathway? | molecules on the surface of microbes, especially endotoxin |
| What are the 2 primary opsonins in bacterial defense? | C3b & IgG |
| Complement factors involved in VIRAL NEUTRALIZATION | C1, C2, C3, C4 |
| Complement factor involved in OPSONIZATION | C3b |
| Complement factors involved in ANAPHYLAXIS | C3a, C5a (allergic response, degranulation of eosinophils) |
| Complement factor involved in NEUTROPHIL CHEMOTAXIS | C5a |
| Complement factors which combine to form the membrane attack complex (MAC) | C5b, C6, C7, C8, C9 |
| People with C1 and C4 deficiencies tend to suffer from what? | rheumatologic and collagen-vascular diseases |
| People with C3 deficiencies are more susceptible to what? | severe recurrent pyogenic sinus & respiratory tract infxns |
| What is a C2 deficiency associated with? | chronic neutropenia |
| Deficiency of C1 esterase leads to? | hereditary angioedema (overactive complement) |
| Deficiency of C6-C8 leads to? | Neisseria bacteremia |
| Deficiency of decay accelerating factor (DAF) leads to? | paroxysmal nocturnal hemoglobinuria (PNH) |
Created by:
Asclepius
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