Biology Reference
In-Depth Information
responses to materials released by the parasite, resulting in a non-specific
inflammatory response that traps and kills the larvae. In which organ and
tissue this might occur in humans is not known, but experiments in mice
indicate that the site of resistance to migrating larvae is probably the
liver,
33
as it may also be in pigs,
34
although other sites, such as the lungs,
where hypersensitivity reactions are possibly most deleterious, must
remain under consideration (see also Chapter 5).
IMMUNOGENETICS AND UNPREDICTABLE
IMMUNE REPERTOIRES
A puzzling early observation in people infected with nematodes
(e.g. Brugia malayi and Ascaris lumbricoides itself) was that, when screened
against complex antigen preparations such as worm homogenates
or excretory/secretory (ES) materials, there was enormous diversity
in protein antigens to which individuals produced antibody
(
Figure 3.3
).
22,26,28,35,36
This was particularly noticeable in ascariasis, in
which people known to be chronically infected, even when related and
living in close proximity, produced diverse antibody repertoires.
35
Thus,
most, if not all, individuals only respond to a subset of the potential
Individual human sera
M
r
(kDa)
12
3
4
5
6
7
8
9
67
43
30
20.1
14.4
FIGURE 3.3
Diversity of immune responses to
Ascaris
antigens by infected humans.
Serum from people known to have long-standing infections with Ascaris lumbricoides were
reacted with radio-labeled antigens of the parasite and then the proteins to which they
produced antibody separated by gel electrophoresis in order to reveal which antigens of the
parasite different people respond to immunologically. This typifies the dramatic diversity in
antibody repertoire between people, even when living in the same environment or even
related. How this arises is not precisely known, but it is most likely to be under the control
of the major histocompatibilty complex (MHC) (see Figure 3.4).
