CD40LG and dengue disease: In this study, we investigated the phenotype and functionality of Tfh cells in acute dengue (acute illness) in patients with varying severity of acute dengue and studied the association of Tfh responses with plasmablast expansion, DENV specific IgM and IgG antibodies, NS1 specific antibodies and DENV serotype specific neutralizing antibody titres to further understand how the functionality and phenotype of Tfh cells associate with expansion of plasmablasts and DENV specific antibody responses in acute dengue infection.