February 1992, Volume 42, Issue 2

Original Article

IMMUNOGLOBULINS AND SERUM PROTEINS IN TOXOPLASMOSIS

Farida Agha  ( Pakistan Medical Research Council, Central Research Centre, Islamabad. )
Agha Sadaruddin  ( Pakistan Medical Research Council, Central Research Centre, Islamabad. )
Abdul Ghafoor  ( National Institute of Health, Islamabad. )

ABSTRACT

Immunoglobulin levels in 47 children (age 13-20 years) with toxoplasmosis were compared with 46 age and sex matched controls. No significant difference was observed in mean serum immunoglobulin (IgG, IgA, 1gM) levels between patients and controls but mean IgM levels were significantly (P) higher in children with acute toxoplasma infection. Total proteins were higher in patients while mean albumin and globulin levels were similar between the two groups. Estimation of serum immunoglobulins in young children with toxoplasmosis has no significance and should not be considered as an immunodiagnostic tool (JPMA 42: 42, 1992).

INTRODUCTION

Human toxoplasmosis, caused by intracellular protozoan parasite toxoplasma gondii, is world wide. Immuno compromised patients are particularly at risk. In Pakistan few studies have been done on the prevalence of toxoplasmosis1-3, but the immune status of patients with toxoplasmosis has not yet been studied. The present study was undertaken to estimate the immunoglobulin levels and serum proteins in patients with toxoplasmosis and to compare the results with age and sex matched healthy controls.

PATIENTS AND METHODS

Forty-seven patients with toxoplasmosis were in­cluded in this study. The toxoplasma gondii IgG an­tibodies were detected using enzyme linked immunosor­bent assay (lab system toxoplasma IgG, ETA). They were further tested for the presence of toxoplasma 1gM antibodies by the same technique. An acute infection was indicated in 12.7% (6/47) IgG positive children. Their sera were assayed for immunoglobulins (IgG, IgA, Igm), total proteins and albumin. The reference values for controls were derived from 46 healthy children matched for age, sex and socio-economic status. The quantitative estimation of immunoglobulins (IgG, IgA, 1gM) was carried out by radial immunodiffusion technique of Mancini4 (Kallasted Laboratories, USA). Serum total proteins was estimated by Biuret method using bio Merieux kit and serum albumin by bromocresol green, BCG (bio Merieux). Statistical analysis was done using Chi square and Students ‘t’ test.

RESULTS

Forty-seven patients with toxoplasmosis were in­cluded in this study, their mean age was 15.1 SE±0.11 years with a range of 13 to 20 years. Of the total, 28 were boys (mean age 15.5±SE 0.15, range 13-20 years) and 19 were girls (mean age 14.6± SE 0.13, range 13-18 years). Forty-six healthy subjects who served as controls were in the same age group. Of 46 controls, 21 were boys and 25 were girls. The mean serum immunoglobulins in patients and controls are shown in Table I.


Though the mean serum IgG and IgA levels were higher in patients than controls but the difference was statistically insignificant.

Table II shows mean serum immunoglobulin levels in patients with acute toxoplasma infection. Out of 47 cases positive for toxoplasma IgG antibody, 6 (12.7%) showed presence of toxoplasma 1gM antibody, which indicated current infection. A significant (P) increase in mean serum 1gM levels was found in patients with acute toxoplasma infection.

Table III shows mean hemoglobin level and serum proteins in patients and controls. Hemoglobin levels in patients were slightly higher than controls. Mean serum total protein was significantly higher (P) in patients but albumin and globulin levels were only slightly elevated in patients than in controls.

DISCUSSION

Protozoal infections caused by unicellular or­ganisms that multiply intra or extra-cellularly in the host, provide a large antigenic stimulus, as in leishmaniasis, trypnosomiasis, malaria, amoebiasis and toxoplasmosis5. Toxoplasma gondii is one of the obligate intra-cel­lular parasites whose infection is usually mild or inap­parent6. The type and degree of the immune response to infection are complex and influence the course of infection, clinical manifestations and its diagnosis. In adolescence and adulthood, most infections are sub­clinical or run a very mild clinical course7. Toxoplasma gondii causes serious illness or death in congenitally infected fetus8-10 and induce a major complication in immune compromised individuals11. Toxoplasmosis is a systemic infection, always ac­companied by the production of serum antibodies at high titre. After the acute stage antibodies persist in lower titres throughout life. Detection of IgM antibodies establishes the diagnosis of recently acquired or reac­tivated infection, but these antibodies soon disappear or decrease to very low levels followed by the appearance of IgG which stays longer. Humoral immunity can be reflected by the levels of plasma proteins, especially the levels of im­munoglobulins. In the present study, patients positive for toxoplas­ma gondli IgG antibodies showed no significant change in serum immunoglobulin levels when compared to controls. No comparable data on serum immunoglobulins in young patients with toxoplasmosis is available. However, in acute or subclinical congenital toxoplasmosis, neonates may exhibit variations in their serologic response to diagnostic antigens as well as alterations in immunoglobulin development12. Some neonates may have an elevation in IgM and IgM toxoplasma antibody. A similar elevation in IgM levels was seen in this study in cases with acute toxoplasma infection (patients showing both IgG and IgM antibodies). It is suggested that the increase in IgM levels in these cases might be due to an intensification of antibody response by the im­munogenic effects of parasite. However, no symptoms were elicited that could reasonably be linked to primary infection in these patients. The raised serum total protein levels could be due to the disease itself or due to some previous infections as some of the cases gave history of hepatitis, typhoid and fever. This study suggests that estimation of im­munoglobulins in toxoplasmosis has no significance and it may not be considered as an immunodiagnostic tool.

ACKNOWLEDGEMENT

We are grateful to Mr. Sheikh Salahuddin for typing the manuscript.

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