Management of infections due to nontuberculous mycobacteria in solid organ transplant recipients-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice.

These updated guidelines from the American Society of Transplantation Infectious Diseases Community of Practice review the epidemiology, diagnosis, prevention, and management of nontuberculous mycobacterial infections in the pre- and post-transplant period. NTM commonly cause one of five different clinical syndromes: pleuropulmonary disease, skin and soft tissue infection, osteoarticular infection, disseminated disease, including that caused by catheter-associated infection, and lymphadenitis. Diagnosis of these infections can be challenging, particularly when they are isolated from nonsterile spaces, owing to their ubiquity in nature. Consequently, diagnosis of pulmonary infections with these pathogens requires fulfillment of microbiologic, radiographic, and clinical criteria to address this concern. A combination of culture and molecular diagnostic techniques is often required to make a species-level identification. Treatment varies depending on the species isolated and is complex, owing to drug toxicities, need for long-term multidrug regimens, and consideration of complex drug-drug interactions between antimicrobials and immunosuppressive agents. Given these treatment challenges, efforts should be made in both the hospital and community settings to limit exposure to these pathogens to the extent feasible.

Active Tuberculosis After Solid Organ Transplantation in Individuals With Negative Pretransplant QuantiFERON-TB Gold Testing: A Case Series.

Active tuberculosis (TB) in solid organ transplant (SOT) recipients most commonly occurs due to reactivation of latent infection and is associated with poor clinical outcomes, including allograft loss and death. National transplant societies, including the American Society of Transplantation, recommend screening for latent TB prior to transplant, with treatment in the peritransplant setting to reduce the subsequent risk of TB reactivation. Though screening is traditionally conducted using laboratory-based assays, such as the QuantiFERON-TB Gold, false negatives may occur in SOT candidates due to anergy from end-stage organ dysfunction, highlighting the need for a multimodal diagnostic approach. In this case series, we describe the clinical characteristics and outcomes of 3 SOT recipients at the University of Pennsylvania with negative pretransplant QuantiFERON-TB Gold testing who subsequently developed active TB in the posttransplant setting, contributing to a growing body of knowledge regarding this challenging population. Each patient experienced a complicated clinical course that arose in part from the lack of diagnosis of TB prior to transplant. Because all had epidemiologic risk factors for TB, the findings of our study highlight the need for more individualized approaches to pretransplant TB screening.

Asymmetric T lymphocyte division in the initiation of adaptive immune responses.

A hallmark of mammalian immunity is the heterogeneity of cell fate that exists among pathogen-experienced lymphocytes. We show that a dividing T lymphocyte initially responding to a microbe exhibits unequal partitioning of proteins that mediate signaling, cell fate specification, and asymmetric cell division. Asymmetric segregation of determinants appears to be coordinated by prolonged interaction between the T cell and its antigen-presenting cell before division. Additionally, the first two daughter T cells displayed phenotypic and functional indicators of being differentially fated toward effector and memory lineages. These results suggest a mechanism by which a single lymphocyte can apportion diverse cell fates necessary for adaptive immunity.

Effector and memory CD8+ T cell fate coupled by T-bet and eomesodermin.

Two seemingly unrelated hallmarks of memory CD8(+) T cells are cytokine-driven proliferative renewal after pathogen clearance and a latent effector program in anticipation of rechallenge. Memory CD8(+) T cells and natural killer cells share cytotoxic potential and dependence on the growth factor interleukin 15. We now show that mice with compound mutations of the genes encoding the transcription factors T-bet and eomesodermin were nearly devoid of several lineages dependent on interleukin 15, including memory CD8(+) T cells and mature natural killer cells, and that their cells had defective cytotoxic effector programming. Moreover, T-bet and eomesodermin were responsible for inducing enhanced expression of CD122, the receptor specifying interleukin 15 responsiveness. Therefore, these key transcription factors link the long-term renewal of memory CD8(+) T cells to their characteristic effector potency.