IMMUNOLOGY

Detailed explanation-1: -Moreover, higher antigen-specific CD4 T-cell numbers accumulated in germinal centres. Our data demonstrate that dendritic cells are sufficient to activate naive CD4 T cells in vivo, but B cells subsequently can enhance CD4 T-cell expansion further.

Detailed explanation-2: -Immune responses are initiated in the T-cell areas of secondary lymphoid organs where naïve T lymphocytes encounter dendritic cells (DCs) that present antigens taken up in peripheral tissues.

Detailed explanation-3: -Indeed, dendritic cells are the only antigen-presenting cells that induce the activation of resting T cells, both in vitro and in vivo. Thus, dendritic cells initiate adaptive immune responses and determine tolerance.

Detailed explanation-4: -Antigen-specific B cells can thus activate naive CD4 T cells if the B cells are also induced to express co-stimulatory molecules.