The impact of splenectomy on antiviral T cell memory in mice

The contribution of the spleen to protective antiviral T cell memory was studied using the mouse model of infection with respiratory syncytial virus (RSV). Virus-specific CD8+ memory T cells were induced by local (intranasal or intracutaneous) or systemic (intravenous) immunization using RSV or vaccinia virus-recombinants expressing an RSV protein. After all three routes of immunization, the spleen was clearly identified as the main anatomic compartment harbouring virus-specific memory T cells. Surprisingly, however, splenectomy performed 30 days after immunization did not impair the efficacy of the memory T cell response to a subsequent RSV challenge infection. Irrespective of the route of priming, splenectomy did not influence the number or the functional activity of virus-specific memory T cells recruited to the lung following RSV challenge. More importantly, splenectomy did not impair pulmonary virus control by antiviral memory T cells in vivo. These findings were confirmed under experimental conditions where no neutralizing antibodies were induced by the priming infection. Thus, although most memory CD8+ T cells localize to the spleen after viral infections, this important lymphoid organ is dispensable for efficient recall responses. These findings have implications for the immunocompetence of splenectomized patients.