Transcript No Slide Title

IMMUNITY PARASITES
MULTIPLE RESPONSES AGAINST PARASITE
eg. cattle responses to Boophilus tick
!
GROOMING
AVOIDANCE
PUSTULE
EOSINOPHILS
ANTIBODY
GRANULOMA
REFRACTORINESS / SUSCEPTIBILITY
• Rhipicephalus sanguineus infected with Babesia canis
IMMUNITY PARASITES
(human is refractory)
grooming
wrong receptors
phagocytosis
• Ixodes ricinus infected with Borrelia burgdorferi
(human is partial refractory / susceptible)
Ab
grooming
evasion of antibody
spirochaetes in
joint
evasion of phagocytosis
IMMUNITY PARSITES
ANTIBODY ON EXTRACELLULAR PROTOZOA
eg. Trypanosoma in blood plasma
Th
B
surface antigen
membrane lysis
C3b complement
+
+ +
+ + +
+
+
+
+
+ +
complement mediated
lysis and opsonisation +
phagocytosis
IMMUNITY PARASITES
IMMUNE EXPULSION OF GUT NEMATODES
stimulatory factors
Th
stimulation of goblet cells
+ type 1 hypersensitivity
releasing mast cell amines
aid expulsion of inactive
worms
B
secretory
antigen
U
U U
antibody
U
gut with goblet cells
nematode inactivation
nematode expulsion
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.
IMMUNITY PARASITES
histamine
serotonin
IgE antibody
attraction of granulocytes
antigen
sensitised mast cell
degranulates when
exposed to antigen
eosinophils
basophils
neutrophils
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
IMMUNITY PARASITES
neutrophils
T cell
macrophage
activation
fibroblasts
antigen
sensitised T lymphocyte
releases lymphokines
lymphocytes
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.
IMMUNITY PARASITES
Th
eosinophil stimulation
antigen
B
Y Y
antibody
FcY
YFc
Y
opsonisation
Fc
degranulation
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
IMMUNITY PARASITES
APC
T cell
antigen
Leishmania in
parasitophorous
vesicle within
macrophage
activated macrophage kills Leishmania
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.
IMMUNITY PARASITES
APC
CTL
CTL
specific
granule release
antigen released
T lymphocyte with Theileria schizont
T lymphocyte killed
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.
IMMUNITY PARASITES
c
Trypanosoma per
mm3 of blood,
variants a - d
d
a
b
a
b
c
d
Titre of antibody to
variants a - d
Time (each peak takes several weeks)