parasite

1. IMMUNITY PARASITES MULTIPLE RESPONSES AGAINST PARASITE
eg. cattle responses to Boophilus tick
!
AVOIDANCE
GROOMING
ANTIBODY
EOSINOPHILS
GRANULOMA
PUSTULE

2. IMMUNITY PARASITES REFRACTORINESS / SUSCEPTIBILITY
• Rhipicephalus sanguineus infected with Babesia canis
grooming evasion of antibody evasion of phagocytosis
• Ixodes ricinus infected with Borrelia burgdorferi
Ab
grooming wrong receptors phagocytosis
(human is refractory)
(human is partial refractory / susceptible)
spirochaetes in
joint

3. IMMUNITY PARSITES ANTIBODY ON EXTRACELLULAR PROTOZOA
eg. Trypanosoma in blood plasma
surface antigen membrane lysis
+
+
+
+
+
+
+
+
+
+
+
+
C3b complement
complement mediated
lysis and opsonisation +
phagocytosis
Th
B

4. IMMUNITY PARASITES IMMUNE EXPULSION OF GUT NEMATODES
U
U
B
Th
U U
secretory
antigen antibody
nematode inactivation nematode expulsion
stimulation of goblet cells
+ type 1 hypersensitivity
releasing mast cell amines
aid expulsion of inactive
worms
stimulatory factors
gut with goblet cells

5. IMMUNITY PARASITES CUTANEOUS HYPERSENSITIVITY - TYPE 1
Types 1 and 4 are both active against mites, ticks, fleas
• TYPE 1 produces amines leading to eosinophil
degranulation protein which is toxic to macro-parasites.
IgE antibody
antigen
histamine
serotonin
eosinophils basophils neutrophils
sensitised mast cell
degranulates when
exposed to antigen
attraction of granulocytes

6. IMMUNITY PARASITES CUTANEOUS HYPERSENSITIVITY - TYPE 4
Types 4 and 1 are both active against mites, ticks, fleas
• TYPE 4 activates macrophages which stimulate
fibroblasts to produce granuloma and neutrophils
to form intra-epidermal pustules
T cell
sensitised T lymphocyte
releases lymphokines
macrophage
activation
neutrophils
lymphocytes
antigen
fibroblasts

7. IMMUNITY PARASITES EOSINOPHILS AGAINST HELMINTHS IN TISSUE
Antibody mediated cytotoxicity against Schistosoma,
Fasciola etc
• Secretory / excretory antigens stimulate production of
antibody from B lymphocytes and eosinophil
stimulation promoter from T lymphocytes.
• Antibody opsonises helminth larva, eosinophils
degranulate around it and kill it.
B
Th
antigen
Y
Y
Y Y
Y Fc
Fc Fc
antibody
eosinophil stimulation
degranulation
opsonisation

8. IMMUNITY PARASITES MACROPHAGE ACTIVATION AGAINST
INTRACELLULAR PROTOZOA (eg Leishmania)
• Type 4 hypersensitivity: antigen stimulates T
lymphocytes to produce interferon gamma. This activates
infected macrophages to produce NO and H2O2 and
extra lysosomal enzymes, all toxic to Leishmania
APC T cell
activated macrophage kills Leishmania
antigen
Leishmania in
parasitophorous
vesicle within
macrophage

9. IMMUNITY PARASITES CYTOTOXIC T LYMPHOCYTES AGAINST
INTRACELLULAR PROTOZOA eg Theileria parva
• Antigen is presented to CTL and they proliferate.
• Antigen + MHC receptors on CTL permit specific
binding to infected lymphocytes.
• Bound CTL release toxic granules to kill infected cell.
T lymphocyte with Theileria schizont T lymphocyte killed
APC
CTL
CTL
antigen released
specific
granule release

10. IMMUNITY PARASITES EVASION OF ANTIBODY BY ANTIGENIC
VARIATION in Trypanosoma
• Trypanosoma antigens stimulate antibody production.
• These antigens can vary in successive generations of
Trypanosoma.
• Each new variant can evade the preceding antibody
response until new antibody is produced.
a
b
c
d
a b c d
Trypanosoma per
mm3 of blood,
variants a - d
Titre of antibody to
variants a - d
Time (each peak takes several weeks)