Malays. Appl. Biol. (December 2000) 29(1&2): 111-119
ENHANCEMENT AND SUPPRESSION OF IMMUNE RESPONSES TO EQUINE HERPESVIRUS TYPE-1 IN MICE DEPLETED OF CD4+ AND CD8+ T-CELLS
MOHD-AZMI, M.L.* and ALI, A.S.
Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
ABSTRACT
The effects of T-cell depletion on antibody and cellular responses against equine herpesvirus type-1 (EHV-1) were studied in mice. In vivo depletion of CD4+ and CDS+ T-cells was effectively done by inoculating BALB/c mice intravenously with anti-CD4 (YTS-169) and anti-CD8 (YTS-191) rat monoclonal antibodies respectively. Results obtained indicate depletion of CD4+ and/or CDS+ T-cells may enhance one type of immune response but immunosuppress others. Thus delayed-type hypersensitivity (DTH) response to EHV-1 as measured by skin reactivity were reduced when CDS+ T-cells depleted but humoral response was enhanced. This indicated that CDS+ T-cells may regulate antibody production to EHV-1 through their suppressive functions. Results demonstrated that DTH response is mediated by both CD4+ and CD8+T cells. In contrast to CD8+ T-cells, CD4+ T-cells were observed to be essential in DTH and humoral responses to EHV-1. Although CDS+ T-cells are not essential but are required to enhance DTH response. Upon challenge infection of immunized mice, the trend showed that the depletion of CD8+ T-cells resulted in an increase of cellular infiltration in lungs and spleens. In contrast, there was no obvious difference between mice depleted only in CD4+ T-cells or both CD4+ and CD8+ T-cells. It is likely that in the absence of CD8+ T-cells, CD4+ T-cells overstimulated cellular infiltration into the lung. Depletion of CDS+ T-cells resulted in higher IgG antibody response but it could not prevent the development of clinical signs of EHV-1 infection. This study showed the best protection against EHV-1 infection could be obtained via involvement of both CD4+ and CDS+ T-cells. These immune cells may block intracellular virus replication and neutralising antibodies block intercellular virus infection.
ABSTRAK
Kesan penghapusan sel T ke atas gerakbalas antibodi dan sel terhadap virus herpes ekuin tip 1 (EHV-1) di kaji dalam mencit. Penghapusan in vivo sel T CD4+ dan CDS+ dilakukan dengan berkesan dengan menyuntik mencit BALB/c melalui intravena masing-masing dengan antibodi monoklon anti-CD4 (YTS-169) dan anti-CDS (YTS-191). Keputusan diperolehi menandakan penghapusan sel T CD4+ dan/atau CDS+ boleh meningkatkan satu jenis gerakbalas imun tetapi imuntindas yang lain. Gerakbalas imun terhadap EHV-1 berkurangan apabila sel T CDS+ dihapuskan tetapi pada masa yang sama liter antibodi meningkat. Ini menandakan sel CDS+ mungkin mengawal produksi antibodi terhadap EHV-1 menerusi fungsi penindasan. Keputusan mempamirkan gerakbalas hiperkepekaan tertunda (DTH) dilakukan oleh sel T CD4+ dan CDS+. Berlainan daripada sel T CDS+, didapati sel T CD4+ adalah penting dalam gerakbalas DTH terhadap EHV-1. Walaupun sel T tidak penting, tetapi diperlukan bagi meningkatkan gerakbalas DTH. Apabila infeksi lawanan diberikan kepada mencit terimun, TREND menunjukkan penghapusan sel T CDS+ mengakibatkan kenaikan infiltrasi sel dalam peparu dan limpa. Sebaliknya, tiada perbezaan ketara diantara mencit yang terhapus sel T CD4+ atau kedua-dua sel CD4+ dan CDS+. Kemungkinan dengan ketiadaan sel T CDS+, CD4+ terlebih rangsang infiltrasi sel ke dalam peparu. Penghapusan sel T CDS+ menyebabkan peningkatan gerakbalas antibodi IgG tetapi gagal menghalang pembentukan tanda klinikal jangkitan EHV-1. Kajian ini menunjukkan perlindungan terbaik terhadap jangkitan EHV-1 boleh diperolehi melalui penglibatan kedua-dua sel T CD4+ dan CDS+. Sel imun boleh menghadang pemreplikatan virus intrasel dan intibodi penutralan manghadang jangkitan virus antara sel.
Key words: EHV-1, T cell depletion, CD4+ T-cells, CDS+ T-cells, IgG antibody.
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