Spindle assembly checkpoint-related meiotic defect in oocytes from LT/Sv mice has cytoplasmic origin and diminishes in older females.

The spindle assembly checkpoint (SAC) ensures proper segregation of chromosomes by delaying anaphase onset until all kinetochores are properly attached to the spindle microtubules. Oocytes from the mouse strain LT/Sv arrest at the first meiotic metaphase (MI) due to, as reported recently, enormously prolonged activity of the SAC. We compared the dynamics of cyclin B1-GFP degradation, the process which is a measure of the SAC activity, in chromosomal and achromosomal halves of LT/Sv oocytes. In chromosome-containing oocyte halves arrested at MI, cyclin B1-GFP was not degraded indicating active SAC. However, in the halves lacking chromosomes, which is a condition precluding the SAC function, degradation always occurred confirming that MI arrest in LT/Sv oocytes is SAC dependent. Transferring the germinal vesicle (GV) from LT/Sv oocytes into the enucleated oocytes from wild-type mice resulted in the progression through meiosis one, indicating that a SAC-activating defect in LT/Sv oocytes is cytoplasmic, yet can be rescued by foreign cytoplasm. These results may help to define the etiology of the human infertility related to the oocyte MI arrest, indicating the involvement of the SAC as likely candidate, and point to GV transfer as the possible therapy. Finally, we found that majority of oocytes isolated from old LT/Sv mice complete the first meiosis. Reciprocal transfers of the GV between the oocytes from young and old LT/Sv females suggest that the factor(s) responsible for the reversal of the phenotype in oocytes from old mice is located both in the GV and in the cytoplasm.

Immune reconstitution after haematopoietic cell transplantation in children: immunophenotype analysis with regard to factors affecting the speed of recovery.

Immune reconstitution was studied prospectively in 66 children who underwent 77 haematopoietic cell transplantations (HCT): 46 autologous HCTs in 39 patients and 31 allogeneic HCTs in 27 patients. We studied the dynamic analysis of immune recovery with regard to potential factors affecting its speed, including age, type of HCT, diagnosis, graft-versus-host disease (GvHD) and cytomegalovirus (CMV) infection reactivation. Absolute counts of different lymphocyte subsets and immunoglobulin serum levels were determined in peripheral blood of patients on d -7 and +16, and then at various intervals up to 24 months post transplant. Common patterns of immune recovery after both allogeneic and autologous HCT were identified: (i) CD4+CD45RO+ peripheral T-cell expansion on d +16; (ii) inverted CD4+:CD8+ ratio from d +30 onwards; (iii) rapid natural killer (NK) cell (CD16+/-CD56+) count normalization. We observed prolonged T-cell lymphopenia (CD3+, CD3+CD4+, CD4+CD45RA+) until 24 months after autologous HCT, whereas in the allogeneic setting CD3+CD4+ cells, including naive CD45RA+ cells, returned to normal values at 9 months post transplant. Age > 10 years and coexistence of GvHD and CMV reactivation were associated with a substantial delay in T- (CD4+, including CD45RA+) and B-cell recovery after allogeneic HCT. Multidrug GvHD prophylaxis resulted in impaired T- (CD4+, CD4+CD45RA+) and B-cell reconstitution only in the early phase after allogeneic HCT (up to 4 months). Our results demonstrated that T-cell recovery was severely impaired in children after autologous HCT. It should be emphasized that specific approaches to enhance immune reconstitution are necessary to control minimal residual disease and avoid the risk of infectious complications in the autologous setting. Thymic involution after allogeneic HCT seems to be associated with age and coexistence of GvHD and CMV reactivation.