<<Disclaimer: Verify this information before applying it to your situation.>>

Deborah recently posted some answers to her questions about reticulin. 
I did not see a spoon though. I really appreciated her humor, so here 
is my version of spoon-feeding. There are two posts:

1. Abbreviations and autoimmunity
2. Immunological assays

Celiac disease is particularly full of abbreviations, starting with 
the name of the disease itself! These are all names for the same 
condition:
CD = celiac disease
DH = dermatitis herpetiformis
GSD = gluten sensitive disease
GSE = gluten sensitive enteropathy

CD is an autoimmune disease, so in order to diagnose it we need to 
look for specific immune activity (production of antibodies) in the 
bloodstream.
Abs = antibodies because antibodies is too long to write out.
Abs may also be referred to as "serological markers" or 
“autoantibodies.”

Ig anything = "immunoglobulin" a fancy name for antibody.
IgG and IgA are two of the five general classes of Abs manufactured by 
the immune system in response to a foreign agent (antigen).

All of the serum (blood) tests for CD are antibody tests. In a person 
with CD, parts of gluten are identified as foreign so the body mounts 
an attack by producing antibodies and a "cascade of immunological 
events" occurs (sorry, no spoon here). Some molecules in our body 
mimic the molecular structure of parts of gluten. So, as part of this 
"cascade of immunological events" (I'm waving my hands) the immune 
system mounts an attack on those parts of the body too. Thus 
autoimmune = attack against self.

Abs are generated in response to: gluten (gliadin in particular), 
enzymes that are overproduced as part of an "inappropriate" reaction 
to gliadin like tissue transglutaminase (tTG), and proteins from part 
of connective tissue or smooth muscle fibers: reticulin and 
endomesium. So, if you have CD you may produce:

anti-gliadin antibodies (AGA),
anti-tTG, anti-reticulin antibodies (ARA),
anti-endomysial antibodies (EMA)
  
BOTH IgG AND IgA antibodies can be generated in response to the 
antigens listed above. The antigen must be indicated along with the 
antibody type. For example: IgA-tTG is the IgA type of anti tissue 
transglutaminase. There is also IgG-tTG. Which one should we look for?

IgG types of tests are more sensitive than IgA but less specific 
(meaning it is readily detected with no problem, but if it is detected 
we cannot say for sure that it is due to CD). IgA types of celiac 
tests are more specific than IgG (more likely due to celiac) but less 
sensitive than IgG (not as readily detected).

IgA is less sensitive partly because some people produce lower levels 
of IgA (they are immunocompromised for some reason). Total serum IgA 
is needed as a background check because 2.6% of celiacs do not produce 
enough IgA to show a positive result (selective IgA deficiency). IgG 
tests can be helpful in the case of IgA deficiency. When background 
IgA levels are normal, the IgA-tTG is the test of choice because it is 
easy to perform, less expensive, and is more sensitive and more 
specific than the AGA types.

The EMA and ARA tests are much less popular.

EMA: Endomysium is the thin connective tissue layer that covers 
individual muscle fibers. Anti-Endomysial antibodies are developed in 
reaction to the ongoing damage to the intestinal lining. In 1997 it 
was found that tissue transglutaminase was the endomysial autoantigen. 
Almost 100% of patients with active CD and 70% of patients with DH 
will have anti-EMA antibodies. The test usually uses monkey esophagus. 
Compared to the other tests it is more expensive, difficult to 
perform, and difficult to standardize.

ARA: This test is not as specific or sensitive as the others. It is 
found in about 60% of CD patients and about 25% of patients with DH.

Visit the Celiac Web Page at Http://www.enabling.org/ia/celiac/index.html
Archives are at: Http://Listserv.icors.org/SCRIPTS/WA-ICORS.EXE?LIST=CELIAC