Memory B lymphocytes could be more prevalent in young children

Vaccination or natural infection enables the production by the organism of antibodies directed against the pathogen (against the SARS-CoV-2 virus, for example). Antibodies are produced by the B lymphocytes which multiply clonally when they encounter the pathogen. Some of these antibodies become long-life memory B lymphocytes that protect the organism against re-infection.

The humoral immune response (that is, the antibody response) may differ between adults and children. In a study, researchers at the University of Stanford, US, analysed how memory B cells against SARS-CoV-2 are distributed through the tissues, as well as the differences between children and adults.

The researchers first of all studied the memory B cell composition of blood samples from children (12 from umbilical cord blood and 93 other blood samples from children aged 1 to 3 years) and adults (114 blood samples from adults aged 17 to 87 years). They also studied the localisation of these memory B cells by analysing the lymph organs of 8 deceased adult donors.

They first of all observed that the children had a higher level of memory B cells reacting against SARS-CoV-2. Their hypothesis was that we are more exposed to other benign coronaviruses during our childhoods and that as a result the activated immune memory enables a cross-reaction against SARS-CoV-2. That would explain why children have less serious forms of COVID-19.

They also observed that in adults, the majority of memory B cells are in the lymph tissues, principally in the lymph glands. Nevertheless, the specific memory B cells from bacteria are more numerous in the spleen. All this information on memory B cells is highly important since vaccination, notably against SARS-CoV-2, depends on their production.