1 - Basic concepts in Immunity Flashcards
Functions of the immune response
- Immunological recognition (innate and adaptive IR)
- Contain infection and if possible eliminate it (via antibodies)
- Immune regulation limits damage to host by immune response
- Generation of immunological memory by adaptive immune system
4 levels of defence of protection
- Anatomic barriers (skin, oral mucosa)
- Compliment/antimicrobial proteins (C3, defensins)
- Innate immune cells (macrophages, NK cells, granulocytes)
- Adaptive immunity (B & T cells)
Innate immunity
Mediated by mechanisms that are in place even before an infection occurs and facilitate rapid responses to invading microbes
Innate immune cells
- Macrophages
- Dendritic cells
- NK cells
- Granulocytes
Adaptive immune cells
- B lymphocytes
- Antibodies
- T lymphocytes
- Effector T cells
Inflammatory response
- Bacteria trigger macrophages to release cytokines and chemokines
- Vasodilation and increased vascular permeability causes redness, heat and swelling
- inflammatory cells migrate into tissue, releasing the inflammatory mediators that cause pain
Cardinal features of an adaptive immune response
Specificity, diversity, memory and self tolerance
Determinants / epitopes
Parts of complex antigens that are specifically recognised by lymphocytes
Clonal selection
Clones of lymphocytes with different specificities are present in unimmunised individuals, and are able to recognise and respond to foreign antigens
Lymphocyte repertoire
The total number of antigenic specificities of the lymphocytes in an individual
What causes the ability of the lymphocyte repertoire to recognise a large number of antigens
Variability in the structures of the antigen-binding sites of lymphocyte receptors for antigens.
Difference between primary and secondary immune responses
Secondary immune responses and more rapid and greater in magnitude
Why is the secondary response typically stronger
- Memory cells accumulate and become more numerous than the naive lymphocytes
- Memory cells react more rapidly and vigorously to antigen challenge compared to naive lymphocytes
Mechanisms that maintain tolerance to self antigens
- Eliminating lymphocytes that express receptors specific for self antigens
- Inactivating self reactive lymphocytes
- Supressessing self reactive cells by actions of regulatory cells
Stages of adaptive immune responses
- Antigen recognition
- Lymphocyte activation
- Antigen elimination
- Contraction (homeostasis)
- Memory
Types of adaptive immunity
humoral and cell mediated
Humoral immunity
B lymphocytes secrete antibodies that prevent infections and eliminate extracellular microbes
Cell mediated immunity
Helper T lymphocytes activate macrophages and neutrophils to kill phagocytosed microbes, or cytotoxic T lymphocytes directly destroy infected cells
Generative lymphoid organs
Bone marrow and thymus
Secondary lymphoid organs
Lymph nodes, spleen, mucosal and cutaneous lymphoid tissues
B lymphocyte lineage pathway
Bone marrow –> blood, lymph –> secondary lympoid organs
T lymphocyte lineage pathway
- Bone marrow –> Thymus –> Blood, lymph –> secondary lymphoid organs.
- Some immature B cells leave bone marrow and complete maturation in the spleen
Active immunity
- Caused by a host response to a microbe or antigen
- Generates immunologic memory
Passive immunity
Caused by transfer of antibodies or T lymphocytes specific for the microbe (e.g. from mother to fetus, vaccine)
Herd immunity
- Occurs when a large portion of a community becomes immune to a disease, making spread unlikely
- Whole community becomes protected
Immune diseases examples
- Rheumatoid arthritis
- Allergy
- Lupus
- Hypothyroidism
- Coeliac disease
Why was smallpox able to be eradicated
- DNA virus that doesn’t change very much
- No animal reservoirs
What are the two major subsets of lymphocytes
B and T cells
Explain adaptive immune response
- Specialised APCs recognise and capture microbial antigens, and display these antigens for recognition by lymphocytes
- Lymphocytes proliferate and differentiate into effector cells
- Effector cells eliminate the antigen and turn into memory cells
Only cells capable of specifically recognising antigens
- Lymphocytes
- Therefore principle cells of adaptive immunity
