2 - Immunity and the immune system Flashcards
what was the first vaccine and who made it
Edward Jenner (“father of immunology”). Used cowpox to vaccinate against the related smallpox virus
Variolation
Samples from smallpox pustules were introduced into healthy individual through nose or skin
What is the only disease to have been eradicated through vaccination
Smallpox
What is the most effective method for protecting individuals against infections
Stimulating immune responses against microbes through vaccination
Immunity
mechanisms used by the body as protection against environmental agents that are foreign
4 functions of the immune response
- Immunological recognition: presence of an infection must be detected
- Contain infection and if possible, eliminate it, via various immune effector functions
- Immune regulation limits damage to the host by the immune response to antigen. Failure of this regulation contributes to abnormal
immune responses and autoimmune diseases - The adaptive immune system generates immunological memory
Immunological memory
Exposure to an infectious agent produces an immune response that can persist, and protect the host in a subsequent exposure
Levels of defence of the body
- Anatomic barriers (Skin, respiratory epithelium, intestine)
- Complement/antimicrobial proteins (C3, defensins)
- Innate immune cells (macrophages, granulocytes, natural killer cells)
- Adaptive immunity (B cells/antibodies, T cells)
Innate immunity
recognition by preformed, non-specific effectors (natural)
Adaptive immunity
Stimulated by exposure to pathogens. Capable of adapting
magnitude and defensive capabilities (specific, acquired)
Examples of innate immunity cells
- Epithelial barriers
- Mast cells
- Phagocytes
- Dendritic cells
Examples of adaptive immunity cells
- B lymphocytes and plasma cells
- T lymphocytes and effector T cells
Haematopoietic stem cells (HSCs)
Give rise to red and white blood cells
First division of HSCs
Myleoid/erythroid progenitor and lymphoid progenitor, then cells with progressively more limited potential
Colony stimulating factors (CSFs) and interleukins
Affect differentiation and maturation
Platelets
Involved in blood clotting and inflammation
Mast cells
Release of granules containing histamine and active agents
Eosinophils
Killing of antibody coated parasites
Neutrophil
Phagocytosis and activation of bactericidal mechanisms
Basophil
Function in inflammatory events and allergies
Macrophage
Ingest and kill foreign cells, participants in immune reactions
Dendritic cell
Process foreign matter and present it to lymphocytes
B cells
- Each B cell expresses a B cell receptor (BCR, membrane bound immunoglobulin) with a unique specificity (identical antigen binding sites)
- Activated B cells can act as professional antigen presenting cells (APC) (present antigen and co-stimulatory molecules to T cells)
Effector B cells
Plasma cells (antibodies producing cells)
T cells
- Each T cell expresses a T cell receptor (TCR)
- Recognises only processed pieces of antigens bound to cell membrane proteins
- Major Histocompatibility Complex (MHC) molecules
Three types of T cells
- Helper T lymphocyte
- Cytotoxic T lymphocyte (CTL)
- Regulatory T lymphocyte
Effect of helper T lymphocytes
- Activation of macrophages
- Inflammation
- Activation of B lymphocytes
Effect of CTL
Killing of infected cell
Effect of regulatory T lymphocyte
Suppression of other lymphocytes
What do Red and white blood cells arise from
stem cells in bone marrow
Where do B and T cells differentiate
- B cells: bone marrow
- T cells: Thymus
(primary lymphoid organs)
Where do haematopoietic stem cells originate
foetal tissues and, in adults, reside primarily in the bone marrow of the axial skeleton
Functions of bone marrow
- Production of blood cells
- Maintenance of HSCs
- Modulation of skeletal remodelling
Thymus
- Thymocytes develop in the bone marrow mature in the thymus, and become T cells
- T cells migrate to peripheral lymphoid organs, where they can be activated
- Atrophy (degeneration) begins at puberty and continues throughout life (lower immunity in elderly)
Where are lymph nodes located
Along lymphatic vessels (drains lymph from tissues back to the circulation
What brings antigens to lymph nodes
Antigen presenting cells (APCs) via lymphatics
Lymph nodes
- Naïve lymphocytes (which have not yet encountered antigen) circulating the blood enter the lymph node and are activated by antigen presenting cells
Spleen
- Trap and respond to blood borne antigens
- Antigens and lymphocytes are carried into the spleen via the splenic artery (not by lymphatic vessels)
Spleen red pulp
Sinuses containing macrophages that phagocytose aged/abnormal erythrocytes and remove microorganisms from the bloodstream
Spleen white pulp
- Lymphoid tissue arranged around central arterioles
- B-cell follicles and periarteriolar lymphoid sheath (PALS), which is populated by T cells
Mucosal associated lymphoid tissue (MALT)
Includes:
- GALT (Gut associated lymphoid tissue)
- BALT (Bronchus associated lymphoid tissue)
- NALT (Nasal associated lymphoid tissue)
- SALT (Skin associated lymphoid tissue)
Autoimmune diseases
Diseases against self
Hypersensitivity diseases
Abnormal immune responses
Myeloid lineage cells
- Neutrophil
- Eosinophil
- Basophil
- Macrophage
- Dendritic cell
- Mast cell
Lymphoid lineage cells
- B and T cells
- Innate lymphoid cells (including natural killer cells)
Secondary lymphoid organs
lymph nodes, spleen and lymphoid tissues associated with mucosa
