Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 23 3 2024 05 27 272 287 Nasrin Noshadi Department of Biology, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran AND Department of Biology, Fars Science and Research Branch, Islamic Azad University, Marvdasht, Iran Ramin Yaghoubi Shiraz Transplant Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Afsoon afshari Shiraz Nephro-Urology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Mohsen Forouzanfar Department of Biology, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran Saeede Soleimanian Allergy Research Center, Shiraz University of Medical Sciences, Shiraz, Iran 2024 01 03 2024 03 28 Reactivation of Polyomavirus BK (BKPyV) is related to reduction of T cells response in kidney transplant recipients (KTRs). Here, we examined the differentiation of CD4+ T cells subsets in response to BKPyV KTRs, using the BKPyV VP1 (viral capsid protein 1) as a stimulator. We categorized our samples into three distinct groups: 1. Reactive BKPyV (BKPyV+), 2. non-reactive (BKPyV-) KTRs and 3. Healthy controls. BKPyV- KTRs and healthy controls stimulated with VP1 and BKPyV+ unstimulated with VP1. The human CD4+ T cells was stimulation with VP1-Ag. The proportion of CD4+ T lymphocytes and their various subsets, including naive T cells, central memory T cells (TCM), and effector memory T cells (TEM) was measured using flowcytometry. BKPyV- KTRs VP1+ indicated significantly lower TCM CD4+ T cells in contrast with both BKPyV+ KTRs VP1-, and healthy controls VP1+. This indicates that VP1 stimulation may reduce TCM cell levels in these patients. The percentage of TEM in the BKPyV- KTRs VP1+ group was significantly less prevalent than the BKPyV+ KTRs VP1- group. The percentage of TEM cells in BKPyV+ KTRs VP1- was significantly lower than the healthy controls VP1+. Stimulation with VP1 protein significantly increased the frequency of cytotoxic CD4+ T cells in BKPyV- KTRs VP1+ compared to BKPyV+ KTRs VP1-. The present research has shown that the VP1 stimulation of CD4+ T cells can induce cytotoxic CD4+ T cells responses that may help overcome BKPyV infection in KTRs. However, VP1 stimulation may also differentially affect TCM and TEM CD4+ T cells subsets. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/3984 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/3984/2073