Dermatophytosis is one
of the most common skin diseases. T-lymphocytes are known
to play a major role
these infections , but the exact mode of action is not
completely clear .
Till recently it was believed that the cytotoxic T cells are acting
against a microbial
agent only if it is presented by human antigen presenting cells ( by the MHC-1
receptor ) . Recently , an assumption has been aroused that there is another mechanism of
cytotoxic effect which is carried out by direct antimicribial activity of the
cytotoxic T cells .
The purpose of our
research was to investigate the direct activity of human peripheral T cells and human skin
derived T cells against Trichophyton rubrum and Trichophyton
mentagrophytes , which are the most common agents causing dermatophytosis .
Peripheral blood mononuclear
cells ( PBMC’s ) were isolated from 15 healthy donors and from 15 chronic
dermatophytic patients .From the skin of 5 healthy donors and from the mycotic
lesion of 5 chronic patients - punch biopsies were taken and skin derived T lymphocytes
were isolated .
All the healthy
patients had acute dermatophytosis in the past which resolved spontaneously. Their
PBMC’s were inoculated in RPMI medium . After proliferation for two weeks in the
presence of Interleukin 2 and antigens derived from these dermatophytes , these
cells were subjected to spores and hyphae from fresh cultures .
The “ killing effect “
of the PBMC’s was evaluated by radioactive chrome test and also by XTT
tetrazolium test after 24h of incubation . Morphological observations were followed
by light microscopy and by scanning (SEM) and transmission (TEM) electron
It was found that in
healthy donors - 95% of the fungal cells from Trichophyton mentagrophytes were not active as a
result of the effect of the peripheral T lymphocytes.
were followed by SEM and TEM . The T lymphocytes were adhered to the hyphae
causing brief damage . In chronic patients no more than 65% of killing was found ,
adhesion was minimal and no dramatic morphological changes were observed .
As for Trichophyton
rubrum - only 50% of the fungal cells were not active in the healthy donors ,
and only about 15% of the fungal cells were damaged in the chronic patients .
The exposure of the T
lymphocytes to antigens like Trichophytin or mitogen like PHA , increased the
cytotoxic effect of the lymphocytes . Concerning the skin derived T cells, the results
were almost the same. Testing the cytotoxic effect of CD-4 cells and CD-8 cells has
surprisingly shown that both groups have a similar effect on the dermatophytes
Our research show ,
for the first time , the possible major mechanism of eliminating a superficial
dermatophyte infection . It has been proved also that this mechanism is defected in chronic
This work may
contribute to develop new medication in chronic dermatophytosis .