{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T06:43:51Z","timestamp":1776235431991,"version":"3.50.1"},"reference-count":48,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T00:00:00Z","timestamp":1776211200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>Acute Lymphoblastic Leukemia (ALL) remains the most prevalent childhood malignancy. While chemotherapy has improved survival rates, multidrug resistance (MDR) mediated by P-glycoprotein (P-gp\/ABCB1) overexpression persists as a major cause of treatment failure and relapse. Natural Killer (NK) cells are pivotal for anti-leukemic surveillance but are often compromised during treatment due to their susceptibility to chemotherapy, a vulnerability intrinsically linked to their own expression of P-gp. Strategies to transiently enhance NK cell chemoresistance could therefore preserve immune function and improve therapeutic outcomes. We hypothesized that stimulating Toll-Like Receptor 2 (TLR2) on NK cells could modulate P-gp expression or activity, enhancing their resilience to cytotoxic drugs.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>In this study, we first characterized NK cells from pediatric ALL patients, confirming the constitutive expression of both the therapeutic target (TLR2) and the drug efflux pump (P-gp) across all major subpopulations. Using a healthy donor model, we then dissected the functional consequences of specific TLR2 heterodimer engagement.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>While agonists for both TLR2\/1 (PCSK) and TLR2\/6 (LTA, MALP-2) induced functional activation, their effects on P-gp were divergent. In a PBMC context, stimulation with the TLR2\/1 agonist PCSK significantly enhanced the efflux of the chemotherapeutic agent Methotrexate (MTX), but not Rhodamine 123. This functional enhancement occurred without increasing P-gp surface expression, suggesting a modulation of transporter kinetics. Crucially, mechanistic assays in purified NK cells revealed that this MTX efflux enhancement relies on the cellular microenvironment, whereas direct high-dose TLR2\/1 stimulation paradoxically led to P-gp loss. Furthermore, we demonstrated that the immunomodulatory effects of PCSK extend beyond chemoresistance to directly potentiate anti-leukemic effector functions; PCSK stimulation significantly enhanced NK cell cytotoxicity against RS4;11 leukemic blasts without compromising effector viability.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion<\/jats:title>\n                    <jats:p>These findings identify a novel immunomodulatory axis where TLR2 signaling differentially regulates P-gp function and effector capacity in NK cells depending on the specific heterodimer engaged and the cellular context. We propose that controlled TLR2\/1 stimulation represents a potential dual-benefit strategy to protect NK cells from chemotherapy-induced suppression while boosting their anti-leukemic activity in ALL.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fimmu.2026.1757205","type":"journal-article","created":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T05:42:35Z","timestamp":1776231755000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["TLR2 activation potentiates P-glycoprotein-mediated methotrexate efflux and enhances cytotoxicity of human NK cells against acute lymphoblastic leukemia"],"prefix":"10.3389","volume":"17","author":[{"given":"Pablo","family":"\u00c1lvarez-Carrasco","sequence":"first","affiliation":[{"name":"Programa de Doctorado en Ciencias Biom\u00e9dicas, Universidad Nacional Aut\u00f3noma de M\u00e9xico","place":["Mexico City, Mexico"]},{"name":"Laboratorio de Investigaci\u00f3n en 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