Organisation of the immune system Flashcards
(32 cards)
Physical barriers for host defence
Skin - mechanical barrier, acidic environment
Mucous membranes - mucus secretions trap microorganisms, cilia expel microorganisms
Physiological barriers for host defence
Body temperature/fever
Low pH in stomach
Chemical mediators - lysosomes, interferons, complement
Cell types of the immune system
T lymphocytes B lymphocytes Antigen presenting cells Neutrophils Eosinophils Basophils Monocytes/macrophages Mast cells Dendritic cells Natural Killer cells
The two major types of T lymphocyte
CD4+ T lymphocytes
CD8+ T lymphocytes
CD4+ T lymphocyte function
T helper cells
Regulatory T cells
- Secrete cytokines
CD8+ T lymphocyte functions
Cytotoxic T cells
- Lyse infected cells
- Secrete cytokines
Process of antigen recognition in T cells
T cells only recognise processed antigen presented at the surface of another cell upon binding with T cell receptor.
Antigen is presented by an MHC molecule after processing.
B lymphocyte features
- Surface antigen receptor is an Immunoglobulin-like structure
- Express MHC class II which present antigen to T helper cells
- Recognised free, intact antigens in body fluids or on cell surfaces
- Use B cell receptor
Role of antigen presenting cells and examples
- Present processed antigens to T lymphocyte to initiate an adaptive immune response
- Dendritic cells
- B lymphocytes
- Macrophages
Roles of neutrophils
Phagocytosis
Killing of microbes
Roles of eosinophils
Phagocytosis
Granule release
Defence against parasitic infections
Roles of basophils
Granule release
May act as APC
Roles of monocytes/macrophages
Phagocytosis
Killing of pathogens
Cytokine release
Acting as APC
Roles of mast cells
Pro-inflammatory granule release
- Secrete histamine and inflammatory mediators such as cytokines
- Can recognise, phagocytose and kill bacteria
- Activation leads to vasodilation and increased vascular permeability
Roles of dendritic cells
Antigen capture
Antigen presentation
Roles of Natural Killer cells
Lysis of infected cells (NOT pathogens)
What are neutrophil extracellular traps
Activated neutrophils release granule proteins and chromatin to form extracellular fibres which trap and immobilise pathogens
Method used to distinguish white blood cells
Cluster of Differentiation
- Uses CD markers
- System differentiates cells based on which antibodies bind to specific molecules expressed on the cell surface
Definition of a primary lymphoid organ
An organ where lymphocytes develop and congregate
Primary lymphoid organs
- Bone marrow, site of B cell maturation and production of immature T cells
- Thymus, site of T cell maturation
Definition of a secondary lymphoid organ
An organ where lymphocytes interact with antigens and other lymphocytes
Secondary lymphoid organs
The spleen
Lymph nodes
Mucosal associated lymphoid tissues (MALT)
Features of the thymus
- Bi-lobed
- Contains whirls of fibroblasts (Hassall’s corpuscles) site of T cell development
- Size decreases with age (atrophy)
- T-cell variation output decreases with age but total output number remains the same
Features of bone marrow
- Site of haematopoiesis
- Increases white blood cell output during acute-phase response
- 2 types, Red and Yellow
- Red marrow = haematopoietic tissue
- Yellow marrow = fatty tissue
