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FIGURE 3.4 Genetic control of the immune repertoire in Ascaris infection and its
unpredictability. Inbred mice of two strains, BALB/c and SJL, were infected with Ascaris
suum, and their serum collected. The antibody in the serum was reacted with radio-labeled
materials secreted by the lung-stage (L3/4) larvae of the parasite, and then analyzed by
protein gel electrophoresis to establish the antigens of the parasite to which the different
strains responded. This diagrammatic representation of the result shows that the two strains
respond to different sets of protein antigens, despite being infected with the same species of
parasite. The density of tone and width of the bands represent strength of recognition of
each component. When the strains of mice are crossed, and their progeny infected and
serum-sampled, the antigen recognition repertoire of their progeny was not predictable
from the responses of their parents. The 14.4 kDa protein is ABA-1. See 23 for further details
and analysis of this phenomenon. See 38 for demonstration that the repertoire is under the
control of the class II region of the major histocompatibility complex (MHC).
protein is particularly stark, in that only one MHC haplotype in mice and
rats (H-2 s and RT1 u , respectively) has so far been found to respond
in infection, 23,24,39,43,44 and responsiveness in humans appears to be
similarly infrequent ( Figure 3.3 ). 22,28
Interest in the immune repertoire to infection is not merely academic,
but can be of direct importance for the effectiveness of immunization. For
instance, it is probable that immunization against nematodes of human
importance will comprise single or a limited cocktail of recombinant
proteins. If people in the immunized population respond heteroge-
neously, then it could be that a significant proportion of vaccinees will fail
to respond sufficiently to be immune. This is recognized as a significant
problem for immunizations that comprise only a single type of protein
(such as for hepatitis, see references in 45 ). What happens in cases where
the same or different pairs of MHC alleles come together in different
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