{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,27]],"date-time":"2026-02-27T03:44:32Z","timestamp":1772163872792,"version":"3.50.1"},"reference-count":20,"publisher":"BMJ","issue":"1","license":[{"start":{"date-parts":[[2022,2,6]],"date-time":"2022-02-06T00:00:00Z","timestamp":1644105600000},"content-version":"unspecified","delay-in-days":5,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003196","name":"Ministero della Salute","doi-asserted-by":"publisher","award":["Ricerca Corrente 2020 and 2021"],"award-info":[{"award-number":["Ricerca Corrente 2020 and 2021"]}],"id":[{"id":"10.13039\/501100003196","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["RMD Open"],"accepted":{"date-parts":[[2021,11,8]]},"published-print":{"date-parts":[[2022,2]]},"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Antibodies against cationic platelet chemokine, platelet factor 4 (PF4\/CXCL4), have been described in heparin-induced thrombocytopenia (HIT), but also in patients positive for antiphospholipid antibodies (aPL) even in the absence of heparin treatment and HIT-related clinical manifestations. Anti-PF4 antibodies have been recently described also in subjects who developed thrombosis with thrombocytopenia syndrome (TTS) in association with adenoviral vector-based, but not with mRNA-based, COVID-19 vaccines.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To investigate whether COVID-19 vaccination affects the production of anti-PF4 antibodies in aPL-positive patients and in control groups.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Anti-PF4 immunoglobulins were detected in patients\u2019 and controls\u2019 serum samples by ELISA and their ability to activate normal platelets was assessed by the platelet aggregation test.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Anti-PF4 were found in 9 of 126 aPL-positive patients, 4 of 50 patients with COVID-19, 9 of 49 with other infections, and 1 of 50 aPL-negative patients with systemic lupus erythematosus. Clinical manifestations of TTS were not observed in any aPL patient positive for anti-PF4, whose serum failed to cause platelet aggregation. The administration of COVID-19 vaccines did not affect the production of anti-PF4 immunoglobulins or their ability to cause platelet aggregation in 44 aPL-positive patients tested before and after vaccination.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Heparin treatment-independent anti-PF4 antibodies can be found in aPL-positive patients and asymptomatic carriers, but their presence, titre as well as in vitro effect on platelet activation are not affected by COVID-19 vaccination.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/rmdopen-2021-001902","type":"journal-article","created":{"date-parts":[[2022,2,7]],"date-time":"2022-02-07T11:39:03Z","timestamp":1644233943000},"page":"e001902","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":8,"title":["Production of anti-PF4 antibodies in antiphospholipid antibody-positive patients is not affected by COVID-19 vaccination"],"prefix":"10.1136","volume":"8","author":[{"given":"Paola Adele","family":"Lonati","sequence":"first","affiliation":[{"name":"Experimental Laboratory of Immunological and Rheumatologic Researches, Istituto Auxologico Italiano Istituto di Ricovero e Cura a Carattere Scientifico, Cusano Milanino, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Caterina","family":"Bodio","sequence":"additional","affiliation":[{"name":"Experimental Laboratory of Immunological and Rheumatologic Researches, Istituto Auxologico Italiano Istituto di Ricovero e Cura a Carattere Scientifico, Cusano Milanino, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mariangela","family":"Scavone","sequence":"additional","affiliation":[{"name":"Department of Health Sciences, Universit\u00e0 degli Studi di Milano, Milano, 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Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0383-9579","authenticated-orcid":false,"given":"Andrea","family":"Lombardi","sequence":"additional","affiliation":[{"name":"Infectious Diseases Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy"},{"name":"Department of Pathophysiology and Transplantation, Universit\u00e0 degli Studi di Milano, Milano, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maria","family":"Gerosa","sequence":"additional","affiliation":[{"name":"Department of Clinical Sciences and Community Health, Universit\u00e0 degli Studi di Milano, Milano, Italy"},{"name":"Division of Rheumatology, ASST Gaetano Pini, Milano, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Franco","family":"Franceschini","sequence":"additional","affiliation":[{"name":"Rheumatology and Clinical Immunology Unit, ASST Spedali Civili di Brescia, Brescia, 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