CD40LG and viral infectious disease: IgA antibodies also play a crucial role against SARS-CoV-2 viral infection since these antibodies are generated shortly after IgM antibodies are secreted, and IgA antibodies serve as the first line of immune defense by preventing SARS-CoV-2 viral particles from infecting several critical regions of the human body such as the respiratory tract, digestive tract, vagina, and so forth (Ma et al., 2020).