basic immunology

what are the key features of an immune response?

- specificity

- memory

- self - nonself discrimination

- redundancy

what does redundant mean in terms of immunology?

if one part fails, another will take over so immunity still happens

what are the features of the innate immune response?

- rapid

- non-sepcific

- no memory

- first line of defence

what are the features of an adaptive immune response?

- slower

- highly specific

- long-lasting memory

- second line of defence

what are the components of the innate immune system?

- skin

- mucosal surfaces

- non-specific antibacterial molecules

- soluble mediators

- cellular mediators

what is an example of a non-specific antibacterial molecule?

lysozyme

what is an example of a soluble mediator in innate immunity?

collectins

what can collectins do? (2)

- opsonise bacteria for phagocytosis

- activate complement

what is a complement in terms of immunity?

an alternative pathway

what can the complements do? (3)

- directly lyses some bacteria

- opsonise bacteria for phagocytosis

- recruits phagocytes

what are examples of cellular mediators?

- neutrophils

- macrophages

- dendritic cells

- natural killer cells

what type of cells are neutrophils and macrophages?

phagocytic cells

how do phagocytes know which are non-self cells?

they use pattern recognition receptors (PRRs)

what do phagocytes do after phagocytosis?

present the antigens of the surface

what triggers the adaptive immune response?

antigen presenting cells

what are the components of the adaptive immune response? (2)

- soluble mediators

- lymphocytes

what are examples of soluble mediators?

antibodies

- IgG

- IgA

- IgM

- IgE

what are the two regions of an antibody?

- Fab region

- Fc region

what is the Fab region? (2)

- Fragment of antigen-binding

- changeable region

what id the Fc region? (2)

- receptor binding

- constant region

what can immunoglobulins do?

bind to extracellular pathogens which:

- blocks their binding to cellular receptors

- activates complement which can kill some pathogens

- labels pathogens for uptake by phagocytosis by Fc region

what are features of IgG specifically?

- secondary response

- can cross placenta (important for babies)

- monomer

- can fix complement

what are features of IgA specifically?

- mucosal immunoglobulin

- cannot fix complement

- dimer

what are features of IgM specifically?

- primary response

- pentameter

- fixes complement

what are features of IgE specifically?

- binds to mast cells (release histamines)

- important in allergy

- monomer

which Ig do naive B cells produce?

IgM

what can specific antigens induce in IgM?

class switching to IgG, IgA or IgE

what are the two pathways to reach complement activation?

- antibody-antigen interactions

- pathogen surface

what is clonal expansion of T and B cells? (2)

- antigen binds to B cells (via antibodies) and T cells with highly specific and complementary receptors

- leads to expansion and differentiation of these clones for generation of memory cells

what happens to the broken down protein antigens?

they are bound by major histocompatibility complex molecules (MHC) or in humans they are called:

human leukocyte antigens (HLA)

what do HLAs do?

present broken down antigens to T cells

how many classes of the HLA gene are there?

2

Class I and II

what makes the HLA genes special?

one of the most polymorphic human genes known

what type of pathogen do Class I HLAs bind to?

endogenous pathogens

(within cells)

what type of pathogen do Class II HLAs bind to?

exogenous pathogens

(extracellular spaces)

what type of cells do Class I HLAs present foreign peptides to?

CD8+ T cells

what type of cells do Class II HLAs present foreign peptides to?

CD4+ T cells

what are CD8+ T cells?

cytotoxic T cells

which peptides do CD8+ T cells recognise?

endogenous peptides in association with Class I HLAs

which peptides do CD4+ T cells recognise?

exogenous peptides in association with Class II HLAs

what are CD4+ T cells?

helper T cells