Innate and Adaptive Immunity Flashcards
What are 4 physical barriers to infection?
Skin
Mucous
Respiratory cilia
Commensal organisms
What are 4 biochemical barriers to infection?
Sebaceous secretions in skin
Lysosome in tears
Spermine in sperm
Gastric acidity
How do most infectious agents enter the body?
Via the mucosal surfaces of: Nasopharynx Respiratory tract Alimentary tract Genito-urinary tract
What’s the definition of an antigen?
A substance capable of inducing an immune response
What are the basic differences between innate and adaptive immunity?
Innate immunity is the primary line of defence, immediate response, recognises certain threats, no antigen presentation and no immunological memory
Adaptive immunity is the secondary line of defence, delayed response, recognises all threats and it has antigen presentation, clonal selection, immunological memory
What do T and B lymphocytes do?
T lymphocytes: cytotoxic, memory, helper, suppressor
B lymphocytes: plasma cells, memory cells
What are Eosinophils, Basophils and Mast cells involved in?
Eosinophils: parasitic infections and allergic responses
Basophils & Mast cells: inflammatory and hypersensitivity reactions
What are the blood cells of the immune system?
Neutrophils Eosinophils Basophils Lymphocytes Monocytes Platelets Erythrocytes
What are some tissues/organs of the immune system?
MALT mucosa associated lymphoid tissue
Thymus where T cells mature
BALT bronchus associated lymphoid tissue
Lymph nodes = small peripheral collections of lymphoid tissue
Spleen = large collection of lymphoid tissue
Kupfer cells in liver = macrophages
Bone marrow is site of haematopoiesis and maturation of B lymphocytes
What type of protein are antibodies and what type of immunity are they involved in?
gamma globulin proteins
Adaptive humoral immunity
What are the 4 humoral components of the immune system?
Acute phase proteins (a, B, y globulins)
Complement (B globulins)
Antibodies (y globulins)
Cytokines (IL, TNF)
What’s phagocytosis?
Recognition and engulfing of microbes, which are then killed by the release of toxic chemicals into the enclosed vacuole
What are the 2 cell types involved in phagocytosis? How are their roles different?
Polymorphonuclear leukocytes (neutrophils) involved in INNATE immunity
Mononuclear phagocyte system (monocytes and macrophages) involved in ADAPTIVE immunity
Outline phagocytosis in innate cell-mediated immunity
- Chemotaxis and adherence of microbe to phagocyte
- Ingestion of microbe by phagocyte
- Formation of a phagosome
- Fusion of phagosome with lysosome to form a phagolysosome
- Digestion of ingested microbe by enzymes
- Formation of a residual body containing indigestible material
- Discharged of waste materials
Outline natural killer cells role in innate cell-mediated immunity
All human cells express MHC Class I molecules on their surface - these are lost in infected/neoplastic cells
NK cells detect the change by lack of stimulation and become activated
Cytotoxicity comes from pore-forming molecules that are inserted into the target cell and cytotoxic molecules are pumped in
What are 4 types of acute phase proteins and what is their role in immunity?
CRP, Ferritin, Alkaline Phosphatase, Pro-Calcitonin
Innate humoral mediated immunity
Pattern recognition receptors bind to pathogen associated molecular patterns = increase in acute phase proteins
Outline the two complement pathways (the complement cascade)
Alternative pathway is antibody independent cell lysis
Classical pathway is cell dependent lysis but both lead to same outcome
C3 cleaved in presence of microbial components
C3a released -> chemotaxis and local anaphylaxis
C3b attaches to microbe -> cleaves C5
C5a released -> chemotaxis and local anaphylaxis
C5b attached to microbe -> activates C6, 7, 8, 9
C5b, C6, C7, C8, C9 = membrane attack complex for cell lysis
Outline MHC and antigen presentation
MHC class I molecules found on all human cells except RBCs MHC class II molecules found only on antigen presenting cells Present antigens from inside host cell
Class I presents host, viral, neoplastic agents to Tc -> cytotoxicity
Class II presents ingested mircobial antigens to Th lymphocytes -> interaction with B lymphocytes to produce antibodies
What different Th lymphocytes do MHC class I and II bind to?
Class II bind to CD4+
Class I bind to CD8+
What cell types are responsible for adaptive cell mediated immunity and adaptive humoral immunity?
Cell mediated: T lymphocytes that are cytotoxic (killer cells)
Humoral: B lymphocytes producing antibodies
Outline adaptive cell-mediated immunity including the different types of T lymphocytes involved
Cell present antigen using MHC Class I to T cytotoxic cells
Those recognising the antigen replicate and differentiate
Tc activity is influenced by T-helper and T-suppressor cells
Tc+ cells attack only host cell presenting antigen
Memory T cells maintain immunological memory
How does each T cytotoxic lymphocyte recognise a single antigen?
Genetic recombination
What does clonal selection and expansion secure?
A specific response and memory (in adaptive cell and humoral mediated immunity)
Outline adaptive humoral immunity
Antigen presenting cells present antigen to T-helper cells
Same antigen stimulates B lymphocytes to replicate and differentiate
B plasma cells produce antibodies that attack only antigen and B memory cells to maintain immunological memory
What are stimulating factors of the immune system?
Presence of antigen
T helper cells
Cytokines
What are inhibiting factors of the immune system?
Removal of antigen
T suppressor cells
Cytokine breakdown
What’s the role of clonal selection and memory cells?
Clonal selection - fine tuning of immune responses (increases/decreases affinity)
Memory cells - improved responses to same antigen in future
Outline the differences between the primary and secondary antibody responses in immunological memory
Primary: Lags 5-10d after immunisation Smaller peak response Antibodies usually IgM>IgG Lower antibody affinity
Secondary: Lags 1-3d after immunisation Larger peak response Relative increase in IgG antibodies (sometimes IgA/IgE) Higher average antibody affinity
How is immunological tolerance controlled?
Negative selection -> deleted
Development of regulatory T cells -> develop in Thymus
What are Interleukins?
12 different proteins produced by mononuclear phagocyte system cells or T helper cells -> stimulate components of immune system for proliferation, differentiation, activation and chemotaxis
Short lived autocrine and paracrine effects
What’s Tumour Necrosis Factor?
Small proteins produced by mononuclear phagocyte system cells -> fever, inflammation, enhanced immunity, septic shock, anorexia, cachexia
What are Interferons?
3 different proteins produced by virus-infected cells and T helper cells, which activate NK and T cytotoxic cells -> lead to cell cytotoxicity and make other host cells virus-resistant
Also activate macrophages and up regulate antigen presentation (integrating with adaptive immune system)
