The Immune System Flashcards
Features of innate immune system
- Always active
- Does not require time for activation
- Response is non-specific to any pathogen
Mucus
Traps potential pathogens, preventing their entry into the body
Skin
Acidic skin secretions inhibit growth of harmful bacteria on skin
Tears & Saliva
Contain lysozymes that kill bacteria
Defensins
Microcidal molecules secreted by skin and mucous membranes
Natural killer cells
Kills human cells that are infected or malignant
Dendritic cells
Phagocytes found in lymph nodes; APC
Phagocytes
Type of white blood cell that can engulf and digest microorganisms, remove dead cells, and boost immune responses
MHC Class I molecule
- Found on all healthy nucleated cells
- Displays peptide antigens in cytoplasm of infected human cells
- Antigen-MHC Class I complex recognized by cytotoxic T cells which kill the target cells
MHC Class II molecules
- Only found on the surface of APCs
- Displays antigens from pathogens digested by APC during phagocytosis
- Antigen MHC Class II complex recognised by helper-T cell
Features of adaptive immune system
- Highly specific to the particular pathogen that induced it
- Immunological memory
- Defends against immune system consists of B & T lymphocytes
Immunological memory
The adaptive immune response increases in magnitude with each subsequent exposure to a particular pathogen
Helper T cells (CD4+ cells)
- Regulates activities of other immune cells via secretion of cytokines
- Express both specific T cell receptors and CD4 receptors
Cytotoxic T cells (CD8+ cells)
- Identifies and kills abnormal human cells in the body
- Express both specific T cell receptors and CD8 receptors
B lymphocytes
- Immature B cells arise from blood stem cells in bone marrow
- Naive B cells differentiate to effector plasma cells or memory B cells
Function of antibodies
- Precipitation
turns soluble antigens insoluble - Agglutination
Links cell bound antigens together, causing clumps - Neutralisation
Masks dangerous parts of pathogens - Inflammation
Triggers histamine release - Complement
Complement protein perforates cell membrane
Somatic recombination
Rearrangement of antigens’s amino acid sequence to confer different antigen specificity
Active immunity
- From exposure to a pathogen or vaccine activates the adaptive immune system to produce antibodies
- Provides long term protection due to production of memory cells
Passive immunity
- Provided when a person is given antibodies (rather than producing it themselves)
- Shorter team protection as antibodies are eventually broken down and are not replenished naturally
