dc.description.abstract | Studies were conducted to evaluate immune associated cellular phenotypes in the lesion areas
ofvervet monkeys (Cercopithecus aethiops) experimentally infected with Leishmania major.
Different immune associated cell types recruited into the lesion sites as a result of primary,
secondary infections were characterized using established cross reactive antihuman
monoclonal antibodies in combination with the immunoperoxidase methods.
Nine adult vervet monkeys were used in this study. The primary infection group consisted of 4
adult naive animals of either sex. The secondary infection group also consisted of 4 adult
animals of either sex which had self cured from experimental L. major infection. One extra
naive control animal was also included. Animals in both groups were inoculated with 5x107
stationary phase promastigotes of L. major and observed after every 2 weeks for lesion
development. Samples from the skin and draining lymph node were obtained at six weeks post
infection and used for staining.
Studies from non infected areas taken as control'skin sections in all the animals revealed the
presence of resident CD8 positive T cells both in the epidermis and dermal layers of the skin.
These (CD8 positive T cells) were smooth in morphology with majority being in the dermal
layer.
B cells, CD 16 and CD4 positive cells were virtually absent in the normal skin while there was
a negligible population of macrophages. These cells, including the keratinocytes only
expressed MHC class 1 antigens.
A heavy cellular infiltration consisting primarily of mononuclear cells was observed at the
lesion sites in both primary and secondary infection groups. Majority of these cells expressed
both MHC class 1 and 2 and the CD8+ phenotypes. The main cell type in the infiltration was
CD8 positive T cell. CD 16 positive cells were also recruited into the lesions and these had a
Lymph nodes draining the control skin sites recorded a lower population of cells than those
draining lesions. Majority of these cells were both MHC class 1 and 2 positive. There
continued to be a higher population of CD8 positive T cells than both B cells and CD4
positive T cells. The difference in CD 16 positive cells between nodes draining control sites and
lesions was not clear. In general, cellular changes occurring in the skin were reflected in the
draining lymph nodes in both infection groups. Nodes draining lesion sites were enlarged, a
feature not observed in those draining control sites.
There were positive delayed type hypersensitivity (DTH) reactions in animals with active
infection and those that had self cured. This indicated that the experimental animals developed
cell mediated immunity. The results show that the CD8+T cell phenotype is the main c.elltype restricting parasites to
the lesion site in both primary and secondary L. major infection in vervet monkeys. The results
.also
show that cellular phenotypes expressing CD3, CD8, CD16 and MHC classes 1 and 2
antigens restricted parasites to the lesion site in both primary and secondary L. major
infections in vervet monkeys. | en |