ISOLATION AND CHARACTERIZATION OF DENDRITIC CELLS FROM MOUSE HEART AND KIDNEY

Dendritic cells (DC) are thought to be distributed throughout lymphoid and most nonlymphoid tissues. Single cell suspensions were prepared f rom mouse hearts and kidneys. Subsets of MHC class Ii-positive (la(+)) leukocytes from both sources expressed markers such as CDw32 Fc recep tors, F4/80, and complement receptor type 3 (CD11b/ CD18). The capacit y of these cells to initiate primary in vitro immune responses was ass essed using oxidative mitogenesis and allogeneic mixed leukocyte respo nses. After fractionation by density centrifugation, cell sorting, imm unomagnetic bead separation, or cell panning, the stimulatory activity of kidney cell suspensions was found to reside in the low density, la (+) leukocyte fractions after overnight culture (day 1). In contrast, freshly isolated (day 0) cells had considerably less or no activity in these assays. However, depletion of la(+) or CD45(+) cells on day 0 f ollowed by overnight culture removed the stimulatory activity on day 1 . Therefore, day 0 kidney cells contain la(+) leukocytes that can acqu ire or up-regulate their stimulatory activity during overnight culture . Similar observations were made for cells isolated from hearts, excep t that a population of uncharacterized nonleukocytes with stimulatory activity was detected on day 0 but not day 1. The phagocytic capacity of the leukocytes was then examined. Subsets of la(+) cells phagocytos ed zymosan, as shown by two-color flow cytometry and other immunofluor escence studies, and the zymosan-positive cells from kidney were able to initiate primary responses. Overall, these data demonstrate the exi stence of DC in kidneys and hearts, and suggest that in situ these cel ls resemble immature rather than mature DC.