COVID-19: What is Humoral immunity? How does it provide prolonged protection?

Researchers have found out that symptomatic patients of COVID-19 have sustained humoral immunity, suggesting prolonged protection from coronavirus infection. A study published in the journal Nature provided an experimental basis for evaluating the onset and duration of humoral immunity among COVID-19 patients to back clinical drug and vaccine development along with decision-making in terms of social-economic mitigation strategies. “Based on our data, it appears that the humoral immune response to SARS-CoV-2 in symptomatic COVID-19 patients is rather prototypical for viruses in having an early expansion phase followed by an intermediate contraction phase and a sustained memory phase,” the researchers wrote.

What is humoral immunity?

In layman terms, humoral immunity is a function of B cells, also known as B lymphocytes, which are a type of white blood cell of the lymphocyte subtype. As per the Science Direct article, the circulating B cell numbers remain constant throughout a person’s life. The spaces outside the cells in the body are protected through humoral immune response in which the antibodies produced by the B cells cause the destruction of extracellular microorganisms and prevent further spread of intracellular infections. (inside the cells).

The activation of B cells and their differentiation into antibody-secreting plasma cells is basically triggered by antigen and usually occurs through T cells or ‘helper T cells. In other words, as explained in NCBI, the B cells with helper T cells lead to the production of antibodies, the affinity maturation of this antibody response, the isotype switching that confers functional diversity, and the generation of memory B cells that provide long-lasting immunity to reinfection.  Humoral immunity is named so because it revolves substances found in the humours, or body fluids.

Immunity after SARS-CoV-2 infection

Another study published in the journal Nature in April 2021 researched the immunity after coronavirus, SARS-CoV-2 infection or COVID-19. The researchers wrote, “T cell responses probably play important roles in the control of SARS-CoV-2 infection, but they have been relatively understudied. Data now suggest that the majority of infected individuals develop robust and long-lasting T cell immunity, which has implications for the durability of immunity and future vaccine approaches.”

“T follicular helper (TFH) cells are thought to play a critical role in providing B cell help and in the formation of humoral immune memory, and circulating populations of these cells that correlate with the development of neutralizing antiviral antibodies have been identified,” the study also said.

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