Immunology Flashcards
What is the difference between INNATE and ADAPTIVE immunity?
Innate immunity
- defence mechanism present from birth
- non-specific (i.e. same response occurs towards many different pathogens)
Acquired immunity
- induced by the presence of ‘foreign’ or ‘non-self’ material
- response unique to the specific substance or pathogen
What immune cells are involved in the NON-SPECIFIC innate immune system
- Macrophages
- Mast Cells
- NKCs
- Neutrophils
What physical barriers does our body already have to prevent infection?
- Skin
- Mucous membranes (Resp, GI and GU tracts)
What are the Primary Lymphoid Tissues of the body and what is their main function?
Bone Marrow and Thymus
=> Anatomical sites where white blood cells (leukocytes) are produced
How are pathogens removed from the lymphatic circulation?
- lymph filtered at lymph nodes
- pathogens are trapped in node before the fluid is returned to venous circulation
- specialised WBC’s used to destroy the pathogens
What aids lymph fluid transport in the body?
Lymph flow = similar to venous flow => requires valves to keep it flowing back to venous angles
- Breathing
- Muscle contractions
- Pulsation in the arteries
- External compression including:
- Manual lymphatic drainage
- Short stretch bandages
- Gradient compression garments
Where in the body can secondary lymphoid tissues be found and what is their function?
- lymph nodes
- tonsils
- spleen
- Peyer’s patches
- Mucosa Associated Lymphoid Tissue (MALT)
- all filter and monitor content of ECF
- lymphocytes areactivated here during adaptive immune response
- all tissues contain distinct zones for different types of lymphocytes (T cells vs B cells)
What WBCs are derived from a myeloid lineage?
Monocytes => Macrophages and Dendritic Cells
Granulocytes => Neutrophils, Eosinophils and Basophils
What WBCs are derived from a lymphoid progenitor cell?
- T cells
- B cells
- Natural Killer (NK) cells
What types of cell can be killed by can Natural Killer Cells?
- tumour cells
- virally-infected cells
- antibody-bound cells/pathogens
What is the common purpose of Mast Cells, Eosinophils and Bsaophils?
- release highly inflammatory granules and substances when activated
- Important in defence against large antibody-coated pathogens that cannot be phagocytosed (e.g. parasites)
Where are Mast cells found, and where are eosinophils and basophils found in comparison?
- Mast cells = in tissues
- eosinophils and basophils = small numbers in the circulation in healthy, non-allergic individuals
- May be an increase in number in allergic/asthmatic individuals
What function is common to Monocytes, Macrophages and Neutrophils?
- Phagocytosis
=> ingest and kill extracellular pathogens, dead apoptotic cells and small immune complexes - Also source of cytokines which regulate acute inflammatory responses
- important at sites exposed to external environment (e.g. skin, mucosal surfaces => Resp, GI, GU tracts)
Where are Monocytes found compared to macrophages and neutrophils?
- Monocytes circulate in the blood
- if they migrate into peripheral tissues they can become tissue-resident Macrophages
- Neutrophils circulate in the blood but are rapidly recruited into inflamed, damaged and infected tissues
What is the function of dendritic cells and where are they most commonly found?
- phagocytosis
- APC to help activate T cells
- present in large numbers in tissues that are in contact with the external environment (e.g. the skin, mucosal surfaces e.g. Resp, GI, GU)
What are the main lymphocyte functions?
B cells - antibody production
CD4+ T cells (helper T cells) - secrete cytokines
CD8+ T cells (cytotoxic T cells) - kill tumour cells and virally-infected cells
What is meant by the “soluble” components of the immune system?
Soluble (humoral) components:
- Complement System (30 proteins produced in liver)
- Cytokines (small proteins and peptides, can act locally or systemically)
Describe the different ways in which cytokines can give off signals
Autocrine signals - signalling cell and the target cell can be the same or a similar cells
Paracrine signalling- to local cells => quick response
Endocrinesignalling- to distant cells => slower, long-lasting response.
What properties make the skin a good barrier to infection?
- tightly packed, highly keratinised, multi-layered cells
- Constantly undergo renewal and replacement
- low pH 5.5 (acidic)
- Sebaceous glands secrete hydrophobic oils, Lysozyme, Ammonia, Antimicrobial peptides to protect
What properties make mucosal surfaces (such as the Resp or GI tract) good barriers to infection?
- Secretory IgA prevents bacteria and viruses attaching to epithelium
- Contains enzymes - Lysozyme, defensins and antimicrobial peptides => directly kill invading pathogens
- Contains Lactoferrin => this starves invading bacteria of iron.
- Cilia trap pathogens and help to remove mucous (assisted by sneezing and coughing)
How can extracellular bacteria and fungi be ingested by macrophages?
Pinocytosis: Ingestion of fluid surrounding cells
Receptor-mediated endocytosis: Molecule bound to receptors is internalised
Phagocytosis: bacteria are internalised whole.
(facilitated by ‘Opsonisation’)
What is opsonisation? What molecules are able to do this?
- Coating of pathogens by soluble factors (opsonins) to enhance phagocytosis
Examples of opsonins:
- C3b
- C-reactive protein (CRP)
I- gG / IgM
How do phagocytes recognise foreign pathogens?
They express Pattern Recognition Receptors (PRRs) on their own cell membrane
These can recognise and bind to Pathogen Associated Molecular Patterns (PAMPs) found on the surface of pathogens
What happens when PRRs on the mast cell membrane bind to PAMPs on a pathogen?
Degranulation => Release of pre-formed pro-inflammatory substances
Gene expression => Production of new pro-inflammatory substances