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Programmed cell death protein 1 (PD-1) is an inhibitory immune receptor involved in immune regulation during infection, but its expression across human B-cell subsets during acute malaria, and its relationship to exposure history and antigen specificity, remain poorly defined.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      PD-1 expression and circulating B-cell subsets were analyzed by flow cytometry in 64 individuals from Uganda and Sweden with different malaria exposure backgrounds, including individuals with acute malaria and healthy controls. PD-1 expression was assessed across major B-cell subsets and compared between\n                      <jats:italic>P. falciparum<\/jats:italic>\n                      -binding and non-binding B cells. Associations with parasitemia and inflammatory markers were also examined.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      PD-1 expression was higher across both na\u00efve and memory B-cell subsets during acute malaria in Ugandan individuals with ongoing malaria exposure compared with individuals with imported malaria diagnosed in Sweden. Within memory B-cell populations, PD-1 frequencies were highest on non-class-switched (IgD\u207a and IgM\u207a) subsets and on\n                      <jats:italic>P. falciparum<\/jats:italic>\n                      -binding B cells. No differences in PD-1 expression were observed between paired acute and convalescent samples. Associations between PD-1 expression, parasitemia, and inflammatory markers were limited and subset-specific.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>\n                      PD-1 expression on B cells during malaria differed according to exposure history and B-cell differentiation state. Broad PD-1 induction during acute malaria was observed only in individuals living in a malaria-endemic setting, and PD-1 expression was enriched among\n                      <jats:italic>P. falciparum<\/jats:italic>\n                      -binding B cells. Together, these findings support a potential role for checkpoint pathways in humoral immune regulation during repeated malaria infections.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s12866-026-05388-8","type":"journal-article","created":{"date-parts":[[2026,7,15]],"date-time":"2026-07-15T08:15:27Z","timestamp":1784103327000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Malaria exposure history shapes PD-1 expression across human B-cell subsets during acute Plasmodium falciparum infection"],"prefix":"10.1186","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5681-2433","authenticated-orcid":false,"given":"Susanne E","family":"Mortazavi","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Allan","family":"Lugaajju","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Muyideen Kolapo","family":"Tijani","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bingyan","family":"Wu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lena","family":"Danielsson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hans","family":"Norrgren","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kristina E M","family":"Persson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,7,15]]},"reference":[{"key":"5388_CR1","doi-asserted-by":"publisher","DOI":"10.30875\/9789287074560","volume-title":"World Malaria Report 2025: addressing the threat of antimalarial drug resistance","author":"World Health Organization","year":"2025","unstructured":"World Health Organization. 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The study was conducted in accordance with the Declaration of Helsinki and relevant national and institutional guidelines and regulations. The study was approved by the School of Biomedical Sciences Research and Ethics Committee at Makerere University and the Uganda National Council of Science and Technology (approvals SBS-REC-765 and HS1267ES), as well as by the Reginal Ethical Review Board in Lund (Dnr 2015\/7) and the Etikpr\u00f6vningsmyndigheten in Stockholm, Sweden (approvals 204\/478\u2009\u2212\u200932 and 2022-03160-01).","order":1,"name":"Ethics","label":"Ethics approval and consent to participate","group":{"name":"EthicsHeading","label":"Declarations"}},{"value":"Not applicable.","order":2,"name":"Ethics","label":"Consent for publication","group":{"name":"EthicsHeading","label":"Declarations"}},{"value":"The authors declare no competing interests.","order":3,"name":"Ethics","label":"Competing interests","group":{"name":"EthicsHeading","label":"Declarations"}}],"article-number":"627"}}