A few months ago I got this information from an LLLL friend; I saved it b/c
my sister (who's nursing a 2 yr old) was being worked up for rheumatoid
arthritis.  I am a bit unhappy to share it because of its conclusions but
here it is for what it's worth - Mary

Mary Renard, RN, BSN, IBCLC
Vienna Virginia  USA

===========================

From March-April, 1998 issue
of Arthritis Today, in the section titled Research Spotlight, 3rd item, p. 20:

"More on the Hormone Connection"
[italics] The link between a milk-producing hormone and autoimmune arthritis
is getting stronger.
   "A large body of circumstantial evidence suggests that prolactin - the
hormone that initiates and maintains milk production in lactating women - is
related to the autoimmune disorders rheumatoid arthritis (RA) and lupus."
   "While women with RA usually go into remission during pregnancy, those
who breastfeed - and, thus, maintain high levels of prolactin longer - are
more likely to have their disease return than new mothers who don't nurse.
Furthermore, abnormally high prolactin levels (not associated with
breastfeeding) have been associated with lupus and have even turned up in
men with RA."
   "Now, new evidence is pointing to a gentic link between prolactin and the
two disorders. The gene that codes for the prolactin hormone is located on
the choromosome 6 - the same chromosome in the same region as the HLA series
of genes, which are believed to play important roles in the body's immune
response."
<snipping out a few paragraphs of technical and genetic stuff that doesn't
seem to relate to breastfeeding>
   "Ollier and his colleagues don't yet know what role the different
prolactin gene subtypes may play in the development of RA or lupus. One clue
is that prolactin, in addition to being produced in the pituitary gland for
its role in lactation, is also made by lymphocytes - a type of white blood
cell involved in the immune process."
"'Prolactin seems to have profound effect in regulating the immune
response,' says Ollier, 'but we won't yet speculate on how that might be
related to these diseases.'"
   "Source: Arthritis and Rheumatism, Vol. 40, No. 8"

My friend who found this article then did a net search and found some other
references:

1.  Rheumatoid arthritis (RA) may be
associated with high blood levels of the hormone prolactin and a
specific HLA gene.... Lancet, 07/13/96

2.  Arthritis & Rheumatism Official Journal of the
American College of Rheumatology VOLUME 40, August 1997,
NO. 8 Special Articles... 10/21/97
Non-profit site:  http://www.rheumatology.org/ar/aug97.html

[From this site:]

Allelic Markers Close to Prolactin are Associated with HLA-DRB1
Susceptibility Alleles Among Women with Rheumatoid
Arthritis and Systemic Lupus Erythematosus

Paul Brennan, Ali Hajeer, Kai Ren Ong, Jane Worthington, Sally John, Wendy
Thomson, Alan Silman, and Bill Ollier 1383

The results of this study suggest that the contribution of prolactin to both
rheumatoid arthritis and systemic lupus erythematosus
might be under control of genes linked to HLA. This raises the possibility
that treatment aimed at reducing the proinflammatory
effect of prolactin may be of value in a genetically determined subgroup of
affected individuals.