The immune response of the mouse to the intestinal trematode Diplostomum phoxini (Faust, 1918)
It was found that starvation of CFLP and NIH mice for six hours prior
to infection was sufficient to produce a marked improvement in the level and
consistency of establishment of oral infections of D. phoxini metacercariae,
if the mice were starved from 6 AN, allowing stomach emptying to occur before
In contrast to spermatogenesis, the detection of vitellogenesis and
oogenesis in D. phoxini in the NIH mouse was markedly delayed compared with
that reported in the duckling.
There was no difference in establishment or loss of a 200 metacercarial
oral infection in male and female NIH mice. Loss began on day 6 and was
complete by day 11 pi. Growth of flukes was complete by day 3. Flukes
were largely confined to the anterior 10 cm of small intestine until the
loss phase, when some attached to the region 10-20 cm post pylorus before
The method used detected a very low rate of egg production which declined
rapidly after the onset of the loss phase of infection, although at this
time there was not a corresponding decline in the percentage of flukes
Implantation of metacercariae into different regions of the small
intestine led to the following conclusions.
1. Establishment was best 30-60 % post pylorus, and very poor in the
posterior 40% of the small intestine. Inconsistent establishment in the
anterior duodenum could be due to lack of preincubation, combined with
2. Recovery of flukes five days after transplantation of metacercariae
was best in those implanted in the anterior 30% of the small intestine and
the percentage of egg bearing flukes was highest in the anterior 10 cm of
3. Flukes that survived until day 5 were the same size if found near to
the site of implantation. Those which had moved in a posterior direction
were smaller.Reduction of infection size from 400 to eight metacercariae resulted
in a four day delay in expulsion of primary infection, which otherwise
occurred normally. Some delay in growth of flukes in a 400 metacercarial
infection may have been due to changes in the gut preceding expulsion.
Cortisone acetate treatment delayed the onset of main fluke loss, which
occurred after day 13 pi, by which time a normal primary infection was
completely removed. 11% of flukes still remained on day 25 pi in treated
mice. It is suggested that this represents loss due to senescence, or to
a delayed, reduced immunological response. Flukes in cortisone acetatetreated
mice were large (comparable to those from low level infections) and
remained in the anterior 10-15 cm of the small intestine. Serial transplantation
also resulted in increased longevity of flukes but losses were greater,
probably due to the trauma of recovery and transplantation.
Transplantation of flukes undergoing expulsion resulted in their reestablishment
in naive donors, though once again losses occurred. Transplanted
flukes then had a longevity similar to that of flukes in an oral primary
The results indicate
1. Expulsion of a primary infection is host-mediated.
2. D. phoxini is highly immunogenic as the expulsion of light infections
(eight metacercariae) is similar to that of infections initiated by
3. Damage to flukes is reversible, as shown by the establishment and
survival of flukes in the process of expulsion, upon transfer to naive
The characteristics of a 200 metacercarial secondary infection
(administered three weeks after a 200 inetacercarial primary infection) are
described. After normal establishment, rejection occurred between two and
four days post infection. Fluke development was impaired, functional
vitellaria did not form and eggs were not produced. Growth stopped before
day 2 pi. No waning of immunological memory occurred when the interval between primary and secondary infections was increased to seven months.
Reduction of the size of the immunizing infection to as few as five
metacercari ae resulted in no reduction in the effect of the immune gut on
the rate of expulsion of secondary infection, although the inhibitory
effect on fluke growth was less marked. Abbreviation of a 200 metacercarial
to 15h duration apparently did not diminish resistance of mice to subsequent
The effects of the immune gut on the growth, development and longevity
of D. phoxini were found to be reversible when flukes from a secondary
infection were transplanted into a naive host.
The effect of the immunized gut on transplanted, almost mature (three
day old) flukes from primary infection was less marked than the effect on
metacercariae surgically implanted into the duodenum, survival of the three
day old flukes in immune mice was almost as long as would be expected in
primary infection, and development proceeded to completion.
Serum from mice infected with D. phoxini eight days previously failed
to transfer immunity. Immunity transferred adoptively by IMLNC was
manifested as an acceleration of expulsion, and a retardation of vitelline
development and reduced growth of flukes in recipient mice compared with
controls. As few as 1x107 IMLNC affected expulsion. 2x107 IMLNC
affected body length and vitelline development also.
IMLNC taken from donor mice between days 2 and 6 of a primary infection
were most effective. After day 6, efficacy declined, however IMLNC taken
from donor mice on day 21 after primary infection unexpectedly had some
effect on recipient challenge infection. IMLNC taken 12 hours after
secondary infection were effective but those from days 6 and 12 of secondary
infection were not. I MLNC transferred less than two days before challenge
of recipient mice did not transfer immunity.
T. lymphoblast activity was high and cellularity of the MLN increased
following primary and secondary infections, but these changes were not coastsknL
correlated temporally with the efficacy of I MLNC. T-lymphoblasts were ineffective but a population of mainly non-dividing B cells was effective
in transferring immunity adoptively.
Histopathological changes in the mouse intestine associated with
D. ph oxini infection were characterized, and the effect of adoptively
transferred immunity (via IMLNC) on these parameters was studied.
Infection was characterized by marked globule leukocyte proliferation
and eosinophilia which preceded and accompanied the expulsion phase of
infection. Both responses occurred more rapidly in secondary than in
primary infection. By comparison, the response of lamina propria mast
cells was delayed and very limited, and was not marked in secondary
The response of goblet cells to infection was minor, and irregular
during normal infection, however it is possible that mucus production
by individual cells may be increased during infection.
Adoptive transfer of immunity led to an acceleration of all cellular
responses. sIg+ve MLNC transferred immunity most effectively and generated
a level of inflammation which was severe compared with normal infection,
and was uncharacteristic as it involved increased goblet cell differentiation.
The poor ability of T cells to transfer immunity might have been attributable
to low viability and/or selective depletion during cell separation.
High variability was observed in the number of plasma cells in the
intestine during infection. The most marked increases occurred in lgG,
and 1gM secreting plasma cells during primary infection and lgG, during