Compare between immune response to protozoa
and helminths
Immune response to
protozoa
Th1: protective ‫مفيدة‬
Th2: counter protective.
Protozoa can be eliminated
by the action of
- Tc
- NK cells
- macrophages.
Immune response to
helminths
Th2: protective ‫مفيدة‬
Th1: counter protective.
Activated Th2 induces:
eosinophilia, IgE production
and mast cells at mucosa.
Helminths are vulnerable to
ADCC involving neutrophil,
eosinophil and macrophages
Helminths resist direct action of
Ab and complement
M.C.Q.
The following helminth can evade the immune system
by antigen disguise:
a- Ancylostoma duodenale c- Schistosoma mansoni
d- Ascaris lumbricoides
b- Enterobius vermicularis
The following parasite can evade the immune system
by cleavage of the produced antibodies:
a- Schistosoma mansoni
c- Trichuris trichiura
b- Giardia lamblia
d- Trypanosoma cruzi
Importance of Immunodiagnosis in Parasitology
Immunodiagnosis is especially important in diagnosis of:
• Visceral larva migrans
Because we cannot precisely locate the parasite.
• Hydatidosis, Trichinosis and Cerebral Toxoplasmosis
Because sampling may be dangerous to the patient.
• Early and Chronic phases of infection
Because parasitic stages may not appear in excreta.
• Fascioliasis
To differentiate true from spurious infections.
• In epidemiological studies
Large numbers of specimens can be simultaneously tested.
Immunodiagnosis rely on identification of:
Antibody OR Antigen
Found in serum, body fluids and faeces
Immunodiagnostic Methods
1- Serology: in vitro testing
- Based on reaction between Antigen and Antibody.
- Can detect and quantify parasite Ag in blood, urine
and stool (coproantigen).
- Can detect specific Ab response to parasite Ag.
Ag detection is more useful than Ab detection:
- For diagnosis of infection in immunosuppressed.
- For diagnosis of active infection.
2- Skin tests: used to detect:
Immediate skin reactivity to parasite Ag (15-30 min.)
Delayed skin reactivity to parasite Ag (24-48 hours)
Disadvantages and Limitations of
Immunodiagnosis
• It can give false results due to cross reactivity
between parasites.
• Skin testing can result in hypersensitivity reactions.
Advantages of serological tests over skin testing
Serological tests
Tests are safe (in vitro)
More sensitive and specific
Easy to differentiate between
old and recent infection
Skin testing
Anaphylaxis may occur
Less sensitive and specific
Less easy
Give reason
Red cell structure can provide some resistance against
infection with Plasmodia.
Duffy antigen
Absence of Duffy antigen: Duffy antigen present
on RBCs acts as a receptor for Plasmodium vivax.
Its absence limits infection with this parasite.
Haemoglobin S: its presence in RBCs provides
immunity against Plasmodium falciparum
because the parasite cannot feed on
this type of haemoglobin.
Deficiency of the enzyme G6PD: This enzyme is needed by
Plasmodium falciparum parasite to develop inside the
infected RBC.
Give reason
Occurrence of nephrotic syndrome complicating
chronic Plasmodium malariae infection.
Due to the deposition of antigen-antibody complexes
(immune complexes) which are deposited on the
basement membrane of the Kidney.
Such immune complexes activate the complement
system resulting in host tissue damage.
Bronchial asthma
Means: difficulty in breathing
Parasitic infections that may be associated with
bronchial asthma:
Cause of bronchial asthma:
1- Fascioliasis.
2- Ascariasis.
3- Ancylostomiasis.
An allergic reaction to
parasite antigens and
metabolites
Mediated by IgE
4- Visceral larva migrans.
5- Bodies of living and dead mites and their excreta.
How Parasites Produce Bronchial asthma
Parasite antigens and
metabolites are released
IgE
is produced
Fab
Fc
Eosinophil
Mast cell
Mediators
Broncho-spasm
Application of molecular techniques in
Parasitology
1- Classification of Parasites.
2- Studying the biology of Parasite.
3- Development of new drugs.
4- Diagnosis of difficult cases.
5- Vaccine development: safe, protective, cheap,
easy to transport and store.
6- Helping Epidemiology and Control measures: by
studying the various strains of the parasites to
get ready by the suitable control measures.