טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentWaldman Arie
SubjectThe Function of T Lymphocytes from Peripheral Blood and
Mycotic Lesion - in Acute and Chronic
Dermatophytosis
DepartmentDepartment of Medicine
Supervisors Dr. Israela Berdicevsky
Professor Emeritus Amos Gilhar


Abstract

Dermatophytosis is one of the most common skin diseases. T-lymphocytes are known to play a major role in curing 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 microscopy .

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.

These observations 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 patients .

This work may contribute to develop new medication in chronic dermatophytosis .