Microbial Pathogenesis 1991 ; 10 : 343-350

Kinetics of intraepithelium and lamina propria lymphocyte responses during Giardialamblia infection in mice V . K . Vinayak,* R . Khannat and Kum Kumt Division of Experimental Parasitology and Parasitic Immunology, Department of Experimental Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh- 160 012, India (Received May 24, 1990 ; accepted in revised form January 12, 1991)

Vinayak, V . K . (Division of Experimental Parasitology and Parasitic Immunology, Dept of Experimental Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh160 012, India), R . Khanna and K . Kum . Kinetics of intraepithelium and lamina propria lymphocyte responses during Giardia lamblia infection in mice . Microbial Pathogenesis 1991 ; 10 :343-350 . The responses of intestinal T-cell subsets and immunoglobulin containing cells were assessed during the course of experimental Giardia lamblia infection in inbred NMRI mice . Quantitation of T-cell subsets in intraepithelium (IEL) and lamina propria (LPL) revealed increased influx of Lyt 2 .2' (suppressor/cytotoxic) T cells and Thy 1 .2* T cells during the establishment (3-5 days post-inoculation) and peak (9-11 days post-inoculation) phases of infection . The influx of these cells reduced as the parasite load declined . In contrast, no significant change was noticed in lamina propria and intraepithelial L3 T4` (helper/inducer) T cells during the establishment or acute phases . However, these cells increased significantly in the decline phase (17-21 days post-inoculation) of infection . The lamina propria IgA-containing cells significantly declined during the establishment and acute phases of infection, and increased significantly as the parasite load in the jejunum declined . Helper/inducer ratios of 0 .4 for IEL and 2 .0 for LPL accompanied the decline of G. lamblia trophozoites in the gut . Our data thus suggest that induction of helper/inducer T cells during the decline phase of infection concomitant with an increase in lamina propria IgA-containing cells resulted in elimination of G . lamblia trophozoites from the gut . Key words : Giardia lamblia ; trophozoite load ; intraepithelial lymphocytes ; lamina propria lymphocytes ; helper/inducer T cells ; suppressor/cytotoxic T lymphocytes; clearance of infection .

Introduction

Giardia lamblia, a protozoan flagellate parasite, has often been implicated as one of the causative agents for diarrhoea and malabsorption' Z especially in children . 3 Although

G . lamblia primarily resides in the small intestine, the perturbations of gut-associated immune responses that allow the progression of disease in the host are poorly understood . Such investigations are difficult to undertake in the human host . Experimental infection in weanling or suckling mice

by

G . lamblia provides models for

* Author to whom correspondence should be addressed . t Present address : Department of Microbiology and Immunology, University of Adelaide, South Australia 5001, Australia . 0882-4010/91/050343+08 $03 .00/0

(c 1991

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human giardiasis . 4 ' Earlier studies from this laboratory 7 ' and others indicated that the immunocompromised hosts had an impaired capacity to eliminate giardial infection from the intestine . Studies have indicated that the clearance of G . muris infection in mice requires activation of helper/inducer T lymphocytes ." , " Therefore, the failure of the immune effector system in the gut is likely to hinder the clearance of giardial infection . The immune alterations at gut levels during establishment and colonisation of the parasite and the subsequent development of the effector immune responses resulting in the clearance of G . lamblia trophozoites from the gut need to be clearly defined . The present study was thus designed to elucidate the responses of intraepithelium (IEL) and lamina propria (LPL) leucocytes during establishment, peak and decline phases of experimental G. lamblia infection in mice .

Results Trophozoite counts The trophozoite load in G. lamblia, infected animals (Group 1) was 0 .70±0 .18x 10 5 at 3-5 days post-inoculation (PI) and increased significantly (P < 0 .01) to 2 .56±0 .82x10 6 by 9-11 days PI . Thereafter, the parasite load declined to 0 .58±0 .22x10 5 by 17-21 days PI . The duration of the infection was divided into the 'establishment phase' (3-5 days PI), the 'peak phase' (9-11 days PI) and the 'decline phase' (17-21 days PI) . None of the uninfected control animals had any G. lamblia trophozoites [Fig . 1 (a)] . Response of intraepithelial and lamina propria T cells to G. lamblia infection The percentages of intraepithelial T cells (Thy 1 .2+), helper/inducer T cells (L3 T4+) and suppressor/cytotoxic T cells (Lyt 2 .2+) were 42 .51 ±5 .27, 18 .46±5 .09 and 68 .02±6 .09 at 3-5 days PI, respectively, in uninfected animals . No significant change in the percentage of these cells was noted during subsequent follow up of uninfected animals on 9-11 or 17-21 days PI [Fig . 1 (b-d)] . In contrast, the G. lamblia infected mice had a differential response of IEL and LPL T-cell subsets during the course of infection . The influx of intraepithelium and lamina propria Lyt 2 .2 + (suppressor/ cytotoxic T cells) and Thy 1 .2+ (T cells) accompanied the establishment and peak phases of the infection [Figs 1 (b and d) and 2(b and d)] . The quantum of such cells declined significantly as the trophozoite load reduced (P

Kinetics of intraepithelium and lamina propria lymphocyte responses during Giardia lamblia infection in mice.

The responses of intestinal T-cell subsets and immunoglobulin containing cells were assessed during the course of experimental Giardia lamblia infecti...
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