Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 380

Another area of HSCT that has been a focus of several clinical trials involves the improvement in the recovery of the immune system after undergoing HSCT. Restoring the condition of the immune system, particularly in terms of eliciting an immune response that is mediated by T cells, is an essential feature of a competent and active immune system. Initially, T cells are regenerated using the donor’s T cells from peripheral blood. However, subsequent regeneration of T cells occurs in the patient’s body through the process of neogenesis. The rate of T cell regeneration generally varies with the age of the patient, and earlier studies have shown that older patients are more likely to experience a delay in immune recovery. In addition, intensive applications of preconditioning chemotherapeutics can further delay the generation of new T cells. The occurrence of GVHD also decreases the chances of achieving immune recovery at a faster rate.

A clinical trial was thus conducted to monitor the number of donor lymphocyte counts in patients who underwent HSCT in order to establish the influence of specific T cell populations in immune recovery, as well as in the outcome of the transplant procedure. The study population consisted of a total of 220 HSCT patients who have been previously diagnosed with various hematologic cancers. These patients received mobilized hematopoietic stem cells that were HLA-matched with their sibling donors. CD4+ T cells were monitored as indicators of patient survival, as well as chronic GVHD; these cells comprise a subset of T regulatory cells that are responsible in the development of GVHD.

One novel finding of this clinical trial is that when the number of CD4+ T cells was relatively high, patient survival increased, regardless of the age of the recipient patient or the relative donor. This study also emphasized that the quality of the donor tissue is more important than the potential amount of tissue that could be used during an HSCT. However, the proponents of this study explained that it might be possible that these superb outcomes were observed because all donor-recipient pairs consisted of siblings who are HLA-matched and thus it does not provide assurance that the same results could be achieved using mismatched siblings or transplants with low T cell counts.