Læknablaðið : fylgirit - 01.05.1978, Síða 147

Ragnhild Gullberg and Eric Jannerfeldt
Department of Rheumatoiogy and Department .
of Clinical Microbiology, Karolinska sjukhuset,
and King Gustaf Vth Research Institute, Stock-
holm, Sweden
Intestinal infections with shigella, salmonella
and Yersinia enterocolitica are not
seldom accompanied by arthritis. There is also
a well-known association between chronic
inflammatory intestinal diseases, e.g. ulcerative
colitis and Chrohn’s disease, and arthritis.
Moreover, it has been proposed that a patho-
logical intestinal flora, containing large amounts
of Clostridium perfringens type A, might
be of aetio-pathogenetic significance in rheuma-
toid arthritis (14). Intestinal absorption not only
of antigens but also of membrane-active lipophilic
substances might be of pathogenetic importance
(13).
Little is known about the normal mechanisms
that control the complex intestinal flora. Specific
IgA antibodies and unspecific factors such as
lactoferrin and lysozyme might be important host
factors (8).
The large molecular size vitamin Bi2-binding
protein (LBP) present in relatively large amounts
in the specific granules of the granulocytes (12)
and in external secretions, e.g. tear fluid. saliva
and human milk, but absent from cow’s milk,
has also been suggested to have an antimicrobial
function (4,6,9,10,11). Large amounts of vitamin
B12 and particularly B12 analogues are normally
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rlS- 1 57
Uptake of Co-cyanocobalamin
by E. coli incubated with free
(squares) and LBP-bound
(triangles) 57Co-cyanocobalamin
for up to 3 hours.
INHIBITORY EFFECT OF
B12-BINDING PROTEIN ON THE
IN VITRO UPTAKE OF B12 BY
INTESTINAL BACTERIA
produced by microorganisms in the distal parts
of the intestine (2,4). In certain pathological
conditions, e.g. small intestinal stasis syndromes,
there is an overgrowth of a faecal type of flora
in the small intestine (3,15). The B12 - rich
intestinal contents could thus favour microorgan-
isms with a more or less ihsufficient capacity
to synthesise their own vitamin B12 and B12
analogues.
Bi^-uptaking bacteria possess specific binding
proteins for vitamin B12, which seems to be taken
up by the baeteria by a process resembling that
of the cells in higher animais (16,17). This
mechanism requires the presence of ionised calcium
in the medium. Coli, coliforms, bacteroides.
pseudomonas, clostridia, and salmonella take up
Bl2 (2,3,4,5,6,7,15,16,17).
The ability of LBP to compete with B12-
uptaking bacteria for B12 in the medium is
favoured by a high stability in body fluids, even
acid gastric juice, and an extremely high affinity
for vitamin Bi^. Moreover, LBP binds not only
vitamin B12 but also a broad spectrum of Bi2
analogues that are not bound by intrinsic factor.
It has since long been known that protein-
bound B12 in body fluids generally is unavailable
to microorganisms used for microbiological assay
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HOUBS
145