Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.O coronavírus 2 da síndrome respiratória aguda grave (SARS-CoV-2) induz uma síndrome respiratória aguda grave chamada COVID-19. As manifestações clínicas do COVID-19 incluem diarreia, pneumonia, linfopenia, linfócitos esgotados e produção de citocinas pró-inflamatórias. A imunologia faz parte do processo de evolução clínica, mas existem algumas questões em torno da proteção baseada na imunidade: (1) por que algumas pessoas infectadas apresentam apenas sintomas leves da doença ou são assintomáticas; (2) por que as respostas tardias e fracas de anticorpos estão associadas a desfechos graves; e (3) por que a positividade em testes moleculares não representa anticorpo protetor IgG. Talvez as respostas das células T possam ser a chave para resolver essas questões. As células T de memória específicas para SARS-CoV-2 persistem no sangue periférico e podem ser capazes de fornecer informações eficazes sobre imunidade protetora. Os estudos com células T podem ser úteis na elucidação dos caminhos para o desenvolvimento de vacinas, terapias e diagnósticos para COVID-19 e para preencher essas lacunas de conhecimento em imunologia.Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces a severe acute respiratory syndrome that is called COVID-19. Clinical manifestations of COVID-19 include diarrhea, pneumonia, lymphopenia, exhausted lymphocytes, and pro-inflammatory cytokine production. Immunology is part of the process of clinical evolution, but there are some questions around immunity-based protection: (1) why some infected people have only mild symptoms of the disease or are asymptomatic; (2) why delayed and weak antibody responses are associated with severe outcomes; and (3) why positivity in molecular tests does not represent protective antibody IgG. Perhaps T cell responses may be the key to solving those questions. SARS-CoV-2-specific memory T cells persist in peripheral blood and may be capable of providing effective information about protective immunity. The T cells studies can be helpful in elucidating the pathways for development of vaccines, therapies, and diagnostics for COVID-19 and for filling these immunology knowledge gaps.