Effect of graft versus host reaction on cell cycle time in neonatal mouse jejunum

The duration of cell cycle parameters in control mouse jejunum has been compared with that found following induction of a graft-versus-host reaction (GvHR) during the first 3 weeks of postnatal life. Values for tc and tG1 were found to decrease progressively during normal development: estimates for the whole crypt column in 21-day-old mice were approximately half to one quarter those found 6 days after birth 12.1 +/- 0.5 hr and 24.2 +/- 0.3 hr for tc; 2.8 +/- 0.3 hr and 12.1 +/- 0.3 hr for tG1 respectively; (means +/- SE). tS and tG2 were found to remain approximately constant during this period of neonatal development. Injecting foreign spleen cells into 3-day-old mice produced no effect on crypt cell proliferation or cell cycle parameters measured 3 days later. GvHR mice studied 8 days after spleen cell injection, however, showed both an increase in crypt cell proliferation and decreases in the values for tc and tG1 to levels similar to those normally found in 21-day-old control animals (tc 12.4 +/- 0.4 hr and tG1 5.4 +/- 0.4 hr for 11-day-old GvHR mice). The possible mechanism leading to these changes is discussed. The ability of GvHR to stimulate cell proliferation is used in the present work to test the hypothesis that the total number of cell divisions taking place after birth determines the temporal sequence of changes in disaccharidase content produced during neonatal development.