CD40LG and susceptibility to pneumonia measurement: Immunoglobulin also contains a large number of specific antibodies which can resist viruses, bacteria and various pathogenic microorganisms.15,16 A study has suggested that the differentiation and maturity of B lymphocytes is inhibited and the synthesis and secretion of corresponding Ig significantly reduces in the development of severe pneumonia, which can affect the killing effect of humoral immune response on pathogens.17 In children with pneumonia, the secretion of Ig G is the most obvious, the secretion of IgA is slightly reduced, but the secretion of Ig M has no significant changes.