Intended for healthcare professionals


Cellular immune responses to covid-19

BMJ 2020; 370 doi: (Published 31 July 2020) Cite this as: BMJ 2020;370:m3018

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  1. Herb F Sewell, emeritus professor of immunology and consultant immunologist1,
  2. Raymond M Agius, emeritus professor of occupational and environmental medicine2,
  3. Marcia Stewart, lay member and emeritus academic3,
  4. Denise Kendrick, professor of primary care research and general practitioner1
  1. 1University of Nottingham, Nottingham, UK
  2. 2University of Manchester, Manchester, UK
  3. 3De Montfort University, Leicester, UK
  1. Correspondence to: H Sewell herb.sewell{at}

T cells could be valuable allies in pandemic control

Protective and enduring immune responses to viral infections or vaccines usually arise from the combined actions of lymphocytes: B cells (responsible for humoral antibody immunity) and T cells (responsible for cellular immunity and helping B cell responses).

B cells produce detectable antibodies in classes IgM, IgG, and IgA along with lesser amounts of IgD and IgE. For SARS-CoV-2, the causative agent of covid-19, the focus is mainly on IgM, IgG, and IgA antibodies that can neutralise the virus by binding to the spike and other membrane proteins and thus preventing infection.1 Understanding the lesser known roles of T cells and cellular immunity will deepen our insights into covid-19 pathogenesis and help inform both vaccine development and pandemic containment strategies.

An effective immune response to SARS-CoV-2 involves four types or subsets of T cells: T helper cells (CD4) are responsible for cellular immunity and for helping B cells to produce neutralising antibodies; cytotoxic or killer T cells (CD8) directly kill infected cells—aided by helper T cells2; …

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