Immunology

Innate immunity refers to antigen-nonspecific defence mechanisms that a host uses immediately or within several hours after exposure to an antigen

This is the immunity one is born with and is the initial response by the body to eliminate microbes and prevent infection

The acute phase response is an innate body defence seen during acute illnesses and involves the change in plasma concentrations of certain blood proteins

These proteins are called acute phase proteins

A group of proteins, produced by cells in the liver and promote inflammation, activate the complement cascade, and stimulate chemotaxis of phagocytes

Positive and negative APPs

Positive APP concentration increases during inflammation. Positive APPs act as inhibitors or destroyers of micro-organism growth as well as providing feedback on immune function

Negative APP concentration decreases during inflammation

• The rise of APP part of wider response • Includes fever, leucocytosis, increased immune reactivity • Mediated by cytokines and TNF (tumour necrosis factor) released from macrophages • In some chronic diseases can have periodic or continuous evidence of the acute phase response

• Most notable of the cytokines that stimulate the APR are IL-1, IL-6, IL-8 and TNF. • Interleukins released by white blood cells usually CD4+ T lymphocytes as well as monocytes and macrophages • TNF – Tumour Necrosis Factor. Produced by macrophages and amongst other functions works to stimulate the production of C- Reactive Protein (CRP) • Released in response to presence of bacterial products such as lipopolysaccharide.

• Level increases 50,000 fold in response to increased production of IL-6 by macrophages • Binds to phosphocholine receptor on bacteria • Assists in complement binding to cell surface via C1q molecule • Also helps to induce phagocytosis by binding to receptor (opsonisation)

• Produced in the liver • Early AP reactant • Role is to attract immune cells to site of infection

• Serine Protease inhibitor (SERPIN) • Inhibits elastase produced by granules in neutrophil • Stops breakdown of elastic tissue

• Storage protein for iron • Produced to inhibit iron uptake by bacteria

• Binds to haemoglobin • Also reducing iron utilisation by bacteria

• Copper dependent protein that has role in oxidising iron thereby inhibiting bacterial uptake

• Most common protein in serum • Has role in molecular transport and providing colloid osmotic pressure • Less albumin thought to inhibit bacterial growth

• Major iron transport protein • Limits amount of iron for bacterial growth