Nucleolar and functional characterization of lymphocytes following cyclophosphamide treatment.

Profound lymphocyte depletion occurs in thymus, lymph nodes and spleens of normal and thymectomized mice early after a single high sublethal dose of cyclophosphamide. Among individual lymphocytes characterized by the different types of nucleolus, the "non-activable" lymphocytes with micronucleoli are affected most markedly by CY, whereas the proportion of the "active" lymphocytes is increased (up to 70% in the spleens). During the period of regeneration lymphocytes with micronucleoli increase rapidly, the increment thereof is very high on day 14 in the spleens of all mice, and still higher in the blood and lymph nodes of thymectomized animals. During the period of lymphocytopenia, in spite of the increased proportion of the "active" lymphocytes, the ability of residual cells of elicit GVH reactions and to incorporate 14C-uridine decreases. In contrast to changes in the early period, the recovery of the "active" lymphocytes and GVH reactivity, which is still incomplete on day 14, depends on the presence of an intact thymus.