Hello, I'm Steven Sacks, back again to introduce the second part of my talk on complement.
The first part, you will remember, was on the normal function of the complement system
in defence against infection.
I'm back with the second part of the talk, to talk about diseases mediated by complement,
which are either due to underactivity of the complement system in complement-deficient
individuals, or overactivity of the complement system, which is the more common
source of tissue injury.
Let me begin with complement-deficient states, which fortunately are rare though instructive,
because they tell us an awful lot more about normal functions of complement.
In particular the relevance and how important that is, both for the host and also
for the successful elimination of pathogens.
In this slide I've represented the cardinal manifestations of inherited complete
(so homozygous) complement deficiency, which is fortunately rare.
There are two manifestations, in the first (on the left), these individuals get recurrent infections
and repeated immune responses, in the second they form immune complexes.
In this instance in the kidney glomerulus, which when cumulative, develops as renal disease.
This particular example shown is the diffuse form of lupus nephritis.
On the left, you see the aftermath of a meningococcal infection
to which complement-deficient individuals are susceptible,
particularly those with terminal pathway deficiencies.
The lesions are teeming with macrophages and leukocytes,
and those cells are teeming with microorganisms - the diplococci which cause meningococcal sepsis -
a really unpleasant killing disease, often associated with complement deficiency.