Background. The study of alloimmune responses has been limited by a lack of
assays that can track the behavior of alloreactive lymphocytes in vivo. He
re we utilize an experimental system that allows the identification and stu
dy of alloreactive CD4(+) lymphocytes responding to major histocompatibilit
y antigens in vivo.
Methods. Responder mouse lymphocytes were labeled with a fluorescein-based
dye, adoptively transferred into irradiated allogeneic stimulator mice, and
recovered at serial time points for analysis by flow cytometry.
Results. Discrete generations of CD4(+) responder lymphocytes proliferating
specifically in response to allogeneic MHC class II were distinguished by
fluorescein intensity. Successive division of alloreactive CD4(+) lymphocyt
es was traced up to six generations after 60 hr.
Conclusions. This experimental system provides information on the division
kinetics of alloreactive CD4(+) cells. Other applications include immunophe
notyping of alloreactive lymphocyte subsets. Further study of systems such
as this will allow the detailed characterization of how alloimmune response
s are initiated and proceed in vivo.