The effect of rabbit anti-thymocyte globulin induction therapy on regulatory T cells in kidney transplant patients.
BACKGROUND
Prevention of alloreactivity by rabbit anti-thymocyte globulins (rATG) may not only result from immunodepletion but also from the induction of T cells that control allogeneic immune responses. In the present prospective and controlled study, we investigated the effect of rATG on the frequency, function and phenotype of peripheral immunoregulatory CD4+ T cells in kidney transplant (KTx) patients.


METHODS
After transplantation, 16 patients received ATG-induction therapy and triple therapy consisting of tacrolimus, MMF and steroids. The control group (n = 18) received triple therapy only. By flow cytometry, T cells were analysed for CD25, FoxP3, CD127, CD45RO and CCR7. To study their suppressive capacities, CD25bright T cells were co-cultured with CD25(-/dim) effector T cells (Teff) in mixed lymphocyte reactions (MLR), stimulated with donor and third party (3P) antigens.


RESULTS
Pre-transplant levels of FoxP3+CD127(-/low) T cells were 6% of CD4+ T cells. One week post-ATG treatment, no measurable numbers of regulatory T cells were present (P < 0.01). After 4 weeks, the cell numbers of CD4+FoxP3+CD127(-/low) T cells slowly reappeared and thereafter remained low (P < 0.01). At 14 weeks, a significant shift towards the CD45RO+CCR7+ (central memory) phenotype within CD4+FoxP3+ T cells was observed (P < 0.01). At 26 weeks, the proliferative alloresponses of the PBMC and CD25(-/dim) Teff profoundly decreased compared to pre-transplant (P = 0.01 and P = 0.02 respectively), while the regulatory capacity of the CD25bright T cells, of which 90% consisted of FoxP3+CD127(-/low) T cells, remained unaffected. The CD25bright T cells suppressed the anti-donor (94%) and 3P responses (93%).


CONCLUSIONS
Our findings show that rATG therapy does not spare peripheral immunoregulatory T cells in vivo, but after regeneration preserves their suppressive activity.
Sewgobind
Varsha D K D
VD
Department of Internal Medicine, Erasmus MC, University Medical Center Rotterdam, Room Ee563a, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. v.sewgobind@erasmusmc.nl
Kho
Marcia M L
MM
van der Laan
Luc J W
LJ
Hendrikx
Thijs K
TK
van Dam
Thea
T
Tilanus
Hugo W
HW
IJzermans
Jan N M
JN
Weimar
Willem
W
Baan
Carla C
CC
D000328:Adult; D000368:Aged; D000818:Animals; D000961:Antilymphocyte Serum / Q000627:therapeutic use*; D002452:Cell Count; D018920:Coculture Techniques; D004359:Drug Therapy, Combination; D005260:Female; D051858:Forkhead Transcription Factors / Q000378:metabolism; D006084:Graft Rejection / Q000276:immunology* / Q000517:prevention & control*; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D053699:Interleukin-7 Receptor alpha Subunit / Q000378:metabolism; D016030:Kidney Transplantation / Q000276:immunology* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009173:Mycophenolic Acid / Q000031:analogs & derivatives / Q000627:therapeutic use; D010641:Phenotype; D011817:Rabbits; D013256:Steroids / Q000627:therapeutic use; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000473:pathology*; D016559:Tacrolimus / Q000627:therapeutic use
D000961:Antilymphocyte Serum; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D007166:Immunosuppressive Agents; D053645:Interleukin-2 Receptor alpha Subunit; D053699:Interleukin-7 Receptor alpha Subunit; D013256:Steroids; D009173:Mycophenolic Acid; D016559:Tacrolimus