It has "been shown for the first time that isoimmunisation of sows by foetal red cell antigens can occur.
By studies on two sows in a minimal disease pig unit, it
was demonstrated that iso-antibodies were produced to the
blood group factor, Ea, after giving birth to Ea positive
piglets but not after giving birth to Ea negative piglets
alone. Complete and reliable life histories of both sows
were available and the possibility of previous injections
of pig red cells in any form was precluded.
Further studies were carried out on two Ea negative,
Kb negative sows which were mated to an Sa positive, Kb
positive boar. In one of these, anti Ea was boosted after
farrowing as in the previous two cases, while in the other
the anti-Ea titre rose about six weeks before parturition.
In addition anti-Kb was produced in both at the same time
as anti-Ea. A subsequent mating of the first of these to
an Ea negative, Kb positive boar resulted in the boosting of
the anti-Kb titre but not the anti-Ea titre, again after
parturition. Likewise on mating the second sow to an Ea
negative, Kb negative boar, there was little effect on the
anti-Ea and anti-Kb titres either throughout pregnancy or
Two Ea negative gilts and a further Ea negative sow,
all of which had no evidence of red cell iso-antibodies in
their sera were mated to an Ea positive boar. Anti-Sa was
detected in the sera of two of them for the first time after
the subsequent parturition; the third remained negative.
On examining the sera from eighty sows and sixty-seven
boars in the routine typing service carried out by the
Blood Group Research Unit, no antibodies other than anti-A were found in the boars' sera while, in twenty-six per
cent of the sows' sera, red cell iso-antibodies were found
as well as anti-A. All these sows were bred to boars of
the same breed as themselves. Similarly, the sera of
fifty per cent of twenty-four sows which had produced
litters affected with thrombocytopenic purpura and which
were mainly bred to boars of different breeds than themselves, had iso-antibodies present
Of these iso-antibodies, anti-Ea and anti-Eb were the
most prevalent and also present at the highest titres.
Anti-Ee, anti-Pa, anti-Ka, anti-Kb, anti-Kd, anti-La and
anti-Lg were also found but usually at only low titres.
The effect of anti-Ea on the red cells of piglets in
four litters was studied. Although the antibody was
absorbed from the colostrum by all the piglets, it had
little effect on their haematological pictures and no
differences were noted between Ea positive and Ea negative
piglets in the same litter.
All these results support further the hypothesis that
iso-immunisation of sows by incompatible foetal antigens
does occur. In support of this hypothesis a condition of
piglets known as thrombocytopenic purpura has been reported
in several Scandinavian countries as well as in the United
Kingdom. It is considered that iso-immunisation of the
sow by thrombocytes of the foetuses takes place in vitro or
at parturition resulting in the destruction of thrombocytes
in the neonatal piglets after absorption of antibodies from
their dam's colostrum. Four litters affected "by this
condition were studied in detail and clinical symptoms
similar to that described by the other workers were noted.
Two gilts, non-affected members of a litter which
suffered from the condition, were mated to a boar, an
affected survivor of a similar litter. During pregnancy
the gilts were injected with pure thrombocyte suspensions
from the boar. The piglets produced from these matings
had normal thrombocyte counts at birth but a proportion of
them developed thrombocytopenia and purpura similar to that
seen in natural cases within a few hours of receiving
colostrum. However, despite the fact that this condition
was observed in three litters from each of these gilts, a
secondary thrombocytopenia at ten to fourteen days of age,
characteristic of the naturally occurring condition, was
only observed in two piglets in one litter.
Of all techniques investigated the antiglobulin
consumption test was found to be the most satisfactory for
the detection of thrombocyte antigen/iso-antibody reactions.
Using this, the thrombocytes of affected and non-affected
piglets in the litters experimentally affected with
thrombocytopenic purpura, were tested against their dam's
serum. A correlation was demonstrated between the
serological reactions of the piglets' thrombocytes and the
clinical signs of purpura and thrombocytopenia.