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Hello to all,

Karen McKenziewrote:
>
> Is there a lupus:celiac link (there's one with RA, yes?)?
> Is it directly on the same HLA markers or on related markers?
> Is the heritability of this know?

According to the "Primer on Rheumatic Diseases - 10-th Edition", "as
many as 80% of Systemic Lupus Erythematosus (SLE) patients have null
(C4A) alleles irrespective of ethnic background, with homozygous C4a (I
think that should say C4A) deficiency conferring a very high risk for
SLE.  Since C4a (again should say C4A) null alleles are part of an
extended HLA haplotype with the markers HLA-B8 and DR3, the influence
of these class I and class II alleles on disease susceptibility may
reflect linkage disequilibrium with complement deficiency.  SLE is also
associated with inherited deficiency of C1q C1r/a, and C2."

This suggests that one if one is at risk for CD one may also be at risk
for SLE.

The terminology C4A, C4a is quite confusing.  Here is my simple
interpretation:  one may carry up to two types of C4 complement genes
(C4A and C4B).  Each of these will give rise to C4a and C4b
complements.  Those derived from C4A have slightly different structure
(< 1%),function and efficacy within the immune complement system.
Having the C4A null gene predisposes one to immune complex disease.
This is because C4A complements bind more effectively to immune system
complexes than those derived from C4B, hence a null C4A could lead to a
reduction in the clearance of these complexes.

References:

Schumacher, H.R., Klippel, J.H., Koopman, W.J., Primer on the Rheumatic
Diseases, 10-th Edition, Arthritis Foundation, 1993,100-116.

Law, S.K.A., Reid, K.B.M., Complement, IRL Press, 1995, 42-46.

<< DISCLAIMER: Not Medical Advice >>

Regards,

John Dankowych