Dendritic cells (DC) are critical for activating naive T cells in vivo, acting as "nature's adjuvant." This study shows that lipopolysaccharide (LPS) induces maturation and migration of DC from the marginal zone to T cell areas in the spleen. Before LPS treatment, DC in the marginal zone lack markers like M342 and DEC-205 but can process antigens. Six hours after LPS, DC with M342 and DEC-205 markers increase in T cell areas, showing enhanced costimulatory activity and reduced antigen processing. By 48 hours, DC numbers in the spleen decrease, correlating with reduced T cell activation. These findings suggest that LPS triggers DC maturation and migration, leading to colocalization with T cells. DC maturation involves upregulation of costimulatory molecules and downregulation of antigen-processing capacity. The study also highlights the role of B7/CD28-CTLA4 pathways in regulating T cell responses. DC are essential for activating naive T cells, inducing antibody responses, and generating antiviral CTL. In vivo, DC play a key role in initiating immune responses. LPS-induced DC maturation and migration may be part of a feedback mechanism to control inflammatory responses. The study also shows that LPS reduces DC numbers in the spleen, impairing T cell activation. These findings demonstrate that microbial products like LPS regulate DC function, influencing immune responses. The results suggest that DC maturation is a dynamic process, with LPS playing a key role in in vivo maturation and migration. The study provides insights into the regulation of DC function by microbial products and their impact on immune responses.Dendritic cells (DC) are critical for activating naive T cells in vivo, acting as "nature's adjuvant." This study shows that lipopolysaccharide (LPS) induces maturation and migration of DC from the marginal zone to T cell areas in the spleen. Before LPS treatment, DC in the marginal zone lack markers like M342 and DEC-205 but can process antigens. Six hours after LPS, DC with M342 and DEC-205 markers increase in T cell areas, showing enhanced costimulatory activity and reduced antigen processing. By 48 hours, DC numbers in the spleen decrease, correlating with reduced T cell activation. These findings suggest that LPS triggers DC maturation and migration, leading to colocalization with T cells. DC maturation involves upregulation of costimulatory molecules and downregulation of antigen-processing capacity. The study also highlights the role of B7/CD28-CTLA4 pathways in regulating T cell responses. DC are essential for activating naive T cells, inducing antibody responses, and generating antiviral CTL. In vivo, DC play a key role in initiating immune responses. LPS-induced DC maturation and migration may be part of a feedback mechanism to control inflammatory responses. The study also shows that LPS reduces DC numbers in the spleen, impairing T cell activation. These findings demonstrate that microbial products like LPS regulate DC function, influencing immune responses. The results suggest that DC maturation is a dynamic process, with LPS playing a key role in in vivo maturation and migration. The study provides insights into the regulation of DC function by microbial products and their impact on immune responses.