Compare between immune response to protozoa and helminths

Th1: protective مفيدة

Th2: counter protective.

Protozoa can be eliminated by the action of

- Tc

- NK cells

- macrophages.

Th2: protective مفيدةTh1: 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

Immune response to protozoa

Immune response to helminths

M.C.Q.

The following helminth can evade the immune system by antigen disguise:

a- Ancylostoma duodenale

b- Enterobius vermicularis

The following parasite can evade the immune system by cleavage of the produced antibodies:

a- Schistosoma mansoni

b- Giardia lamblia

c- Schistosoma mansoni

d- Ascaris lumbricoides

c- Trichuris trichiura

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 ToxoplasmosisBecause sampling may be dangerous to the patient.• Early and Chronic phases of infectionBecause parasitic stages may not appear in excreta.• FascioliasisTo differentiate true from spurious infections.• In epidemiological studiesLarge 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 Skin testing

Tests are safe (in vitro) Anaphylaxis may occur

More sensitive and specific Less sensitive and specific

Easy to differentiate between old and recent infection

Less easy

Give reason

Red cell structure can provide some resistance against infection with Plasmodia.

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.

Duffy antigen

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:

1- Fascioliasis.

2- Ascariasis.

3- Ancylostomiasis.

4- Visceral larva migrans.

5- Bodies of living and dead mites and their excreta.

Cause of bronchial asthma:

An allergic reaction to parasite antigens and

metabolites

Mediated by IgE

How Parasites Produce Bronchial asthma

Eosinophil

Mast cell

IgE is produced

Parasite antigens and metabolites are released

Mediators Broncho-spasm

Fab

Fc

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.