Amid a viral pandemic such as now, many people are wondering if they will get very sick if they are infected and how long can vaccine protection last. To get some answers, immunologists had to grapple with the enormous complexity of the immune system, with its myriad protective agents and pathways. In almost all discussion, antibodies dominate the conversation. T cells on the other hand, are often ignored or downplayed when in fact, both are critical to the immune response. This post sets the record straight.

Viruses induce the production of antibodies – Y-shaped proteins that bind to the surface of the virus and thus hinders virus entry into cells. If the right antibodies are present in sufficient quantity before an individual is exposed to a virus (because they had been suitably vaccinated), they may be able to escape viral infection altogether.

T cells perform their roles by recognizing fragments of virus proteins that are chopped up inside infected cells which are “presented” on the cell surface (see graphic).

T cells may not be able to completely prevent virus infection from happening, but they can rapidly snub out viral expansion in the body and thus prevent disease. Importantly, they maintain the “memory” of a pathogen for decades and are rapidly summoned upon new infection. For example, in one study, it was found that 23 individuals who had the Sars virus in 2003 were found to have T cells that recognize Sars-Cov-1, the virus that caused Sars, 17 years after infection.

The importance of T cells in fighting viruses is not a new concept. It has been fundamental to the scientific community for over 50 years. But as mentioned, antibodies tend to dominate the discussions due to their more direct link with vaccines. In the present Covid-19 situation, too, the role of T cells was initially largely ignored, partly because T cells are harder to study and some classical vaccines, such as the seasonal flu vaccine, mostly rely on antibody generation. But this is changing. Scientists have begun to recognize the critical role of T cells in the fight against Covid-19 and its many variants.

The latest research findings as of now shows that T cells were primed enough by vaccination that they were able to defend against the Omicron variant [1]. This finding, from Erasmus University in the Netherlands and the University of Cape Town in South Africa, indicate that T cells are the unsung heroes of the immune system, playing a vital role in protecting against severe disease with the omicron variant even when antibodies wane, which may explain why a record wave of infections hasn’t engulfed hospitals so far.

It is now clear that a healthy T cell population complements antibodies in the fight against pathogens, and a healthy T cell response to one viral infection is likely to persist in protecting individuals from subsequent bouts of infections. These discoveries are now spurring efforts to develop vaccines that can generate effective T cell response, not just antibody response.

Notes

[1] “T Cells Come to the Rescue as Studies Show They Buck Omicron”, Bloomberg report, 30 December 2021. Link: What Are T Cells? Studies Show They Protect Against Omicron – Bloomberg