Host defence against infection Flashcards
Summarise the sequence and timing of events during infection; Summarise and give examples of the roles in host defence taken by :physical, chemical and mechanical barriers, antigen presenting cells, immune regulatory mechanisms; Define, explain and compare innate vs adaptive immunity, humoral vs cellular immunity, defence against bacteria, viruses and fungi and defence at mucosa versus the skin
What are the sequential actions of the immune system?
1) Pre-infection: first line defence
- avoidance - mucus - physical barriers
2) Early infection: second line defence
- phagocytes - opsonins - some lymphocytes
3) Late infection: specific/acquired defence
- T cells - Antibodies
What is the role of physical, mechanical and chemical barriers in host defence?
Act as pre-infection body defences
e.g. Skin, Epithelial tight junctions, Low pH in sweat/stomach
What is the role of antigen presenting cells (APCs) in host defence?
Process antigens and present them with MHC II for interaction with T cell receptors
What is the role of interferons in host defence?
Type I/III (alpha/beta/lambda) Activate NK cells, upregulate MHC and induce antiviral state Type II (gamma) stimulates and modulates immune response, causes CD4+ to differentiate into Th1
What are the 6 defences against bacteria?
Surface defences Antibody opsonisation Complement Phagocytosis Release of inflammatory mediators and acute phase proteins Fever
What are the 6 defences against viruses?
Surface defences Interferons Inflammatory mediators and acute phase proteins NK cells Antibody, complement, ADCC T cells
What are the 9 mucosal surface defences?
Mucus CIlia Coughing and sneezing Mucosal lymphocytes Secretory IgA Special antigen sampling Enzymes Antimicrobial peptides Mannan binding proteins
