Regeneration of hematopoiesis after allogeneic hematopoietic cell transplantation (HCT) involves conversion of the recipient's immune system to donor type. It is likely that distinct cell lineages in the recipient reconstitute at different rates. Dendritic cells (DCs) are a subset of hematopoietic cells that function as a critical component of antigen-specific immune responses because they modulate T-cell activation, as well as induction of tolerance. Mature DCs are transferred with hematopoietic grafts and subsequently arise de novo. Little information exists about engraftment kinetics and turnover of this cell population in patients after allogeneic HCT. This study examined the kinetics of DC chimerism in patients who underwent matched sibling allogeneic HCT. T-cell, B-cell, and myelocytic and monocytic chimerism were also studied. Peripheral blood cells were analyzed at defined intervals after transplantation from 19 patients with various hematologic malignancies after treatment with myeloablative or nonmyeloablative preparatory regimens. Cell subsets were isolated before analysis of chimerism. Despite the heterogeneity of the patient population and preparatory regimens, all showed rapid and consistent development of DC chimerism. By day ؉14 after transplantation approximately 80% of DCs were of donor origin with steady increase to more than 95% by day ؉56. Earlier time points were examined in a subgroup of patients who had undergone nonmyeloablative conditioning and transplantation. These data suggest that a major proportion of blood DCs early after transplantation is donor-derived and that donor chimerism develops rapidly. This information has potential implications for manipulation of immune responses after alloge-

Summary. An antigenic analysis was made of echovirus 30 and coxsackievirus B4 isolates by determining neutralization rate constants in neutralization kinetic tests. The seven echovirus 30 isolates included the prototype strain and six others isolated in Melbourne, Australia, between 1959 and 1982. Little antigenic heterogeneity was observed in contrast to the evidence of antigenic variation recorded in similar tests on seven coxsackievirus B4 isolates. These isolates also included the prototype strain, as well as six others isolated in Melbourne between 1958 and 1973. The results obtained with the coxsackievirus B4 isolates were in keeping with those observed particularly with the polioviruses and also coxsackievirus B4 by other workers. Those obtained with the echovirus 30 isolates were unexpected, as this virus is also a member of the enterovirus group.

Two cases of acute non‐haemorrhagic conjunctivitis due to coxsackievirus A24 (CA24) are described. These are the first Australian isolates. The presentation was as a severe conjunctivitis in otherwise healthy adults who had not travelled outside Australia. The course was of short duration and self‐limiting, with no long‐term sequelae. The isolates could not be neutralised by antiserum prepared against prototype CA24 but were identified by immune electron microscopy and complement fixation.