Innate and Adaptive Immunity Flashcards
What are the roles of the immune system?
Immunity to infection
Inflammatory processes
Removal of senescent cells
Defence against neoplasia
Define antigen
A substance capable of generating a specific immune response
Which antigens are mainly targeted by the innate immune system?
Antigens with pathogen associated molecular patterns (PAMPs)
Define innate immune system
Immediate response to an antigen which recognises certain but not all threats. Does not involve clonal selection, antigen presentation or immunological memory.
Primary defence
Define adaptive immune system
Secondary line of defence.
Delayed immune response that recognises all threats. Involves immunological memory, antigen presentation and clonal selection.
What are the different types of barrier immunity?
Give examples
-
Physical barriers:
- Skin
- Respiratory cilia
- Mucus
- Commensal organisms
-
Biochemical barriers:
- Sebaceous skin secretions
- Lysozyme in tears
- Spermine in sperm
- Gastric acidity
How do most infectious agents enter the body?
Via:
- Nasopharynx
- Respiratory tract
- GI tract
- Genito-urinary tract
List the components of the innate cell-mediated immune system
2 main cell types:
-
Phagocytes:
- Neutrophils: polymorphonuclear phagocytes (mostly innate immunity)
- Antigen presenting cells- monocytes and macrophages
- Natural killer cells
Describe the process of phagocytosis
- Chemotaxis and adherence of microbe to phagocyte
- Ingestion of microbe by phagocyte
- Formation of phagosome
- Fusion of phasosome with lysosome: phagolysosome
- Digestion of microbe by enzymes from lysosome.
- Formation of residual body containing indigestible material
- Discharge of waste materials by exocytosis.
Describe the role of natural killer cells
Perform under direct and indriect antibody-dependent cell cytotoxicity (process remains innate).
- Detect loss of MHC class I molecules in infected or malignant cells (normally present on healthy cells) and become activated.
- Inserts pore-forming molecules into target cell and pumps in cytotoxic chemicals resulting in cell lysis.
What are the types of barrier immunity?
Give examples
Physical barriers: skin, respiratory cilia, commensal organisms, mucus.
Biochemical barriers: lysozyme in tears, sebaceous skin secretions, spermine in sperm, gastric acidity.
List the components of innate humoral immunity
Acute phase proteins:
- CRP
- Pro-calcitonin
- Alk phos
- Ferritin
Complement
Describe the acute phase proteins of innate humoral immunity
- Produced in response to PAMPs
- Immediate/ non-specific cytotoxicity
- e.g. CRP, pro-calcitonin, alkaline phosphatase, ferritin.
- CRP binds to surface molecules of bacteria and fungi (not viruses), has some inhibitory effects and promotes complement binding.
- Therefore raised in bacterial and fungal infections but not in viral.
Describe the classic and alternative pathways of complement
What is needed to inhibit these pathways?
- Classic: anti-body dependent cell lysis.
-
Alternative:
- C3 cleaved in presence of microbe
- C3a → chemotaxis and local anaphylaxis inflammation
- C3b → opsonisate of microve, cleavage of C5
- C5a → chemotaxis and local anaphylaxis (inflammation)
- C5b → attaches to microbe and activates C6,7,8 & 9.
- C5b, 6, 7, 8 & 9 = membrane attack complex → cell lysis.
C1 needed to inhibit these pathways.
Which immune cell tends to predominate in acute infections?
What part of the immune system are they part of?
Neutrophils
Innate immunity mostly.
Describe the process of clonal selection
Each T and B lymphocyte are responsive to only one antigen. When that antigen is detected, the T or B lymphocyte with the ‘best fit’ for that specific antigen is selected and replicates.
As it replicates, the antibodies it produces evolve slightly due to genetic recombination. The cell with the most appropriate antibody for that antigen then replicates further ensuring a specific response. (expansion).
