Regulatory T Cells Promote Natural Killer Cell Education in Mixed Chimeras.

Therapeutic administration of regulatory T cells (Tregs) leads to engraftment of conventional doses of allogeneic bone marrow (BM) in nonirradiated recipient mice conditioned with costimulation blockade and mammalian target of rapamycin inhibition. The mode of action responsible for this Treg effect is poorly understood but may encompass the control of costimulation blockade-resistant natural killer (NK) cells. We show that transient NK cell depletion at the time of BM transplantation led to BM engraftment and persistent chimerism without Treg transfer but failed to induce skin graft tolerance. In contrast, the permanent absence of anti-donor NK reactivity in mice grafted with F1 BM was associated with both chimerism and tolerance comparable to Treg therapy, implying that NK cell tolerization is a critical mechanism of Treg therapy. Indeed, NK cells of Treg-treated BM recipients reshaped their receptor repertoire in the presence of donor MHC in a manner suggesting attenuated donor reactivity. These results indicate that adoptively transferred Tregs prevent BM rejection, at least in part, by suppressing NK cells and promote tolerance by regulating the appearance of NK cells expressing activating receptors to donor class I MHC.

Necrotizing fasciitis in infancy: an uncommon setting and a prognostic disadvantage.

Necrotizing fasciitis is a potentially fatal, progressive soft tissue infection that typically occurs in adults, and only rarely occurs in infants. Although adults in whom necrotizing fasciitis develops are commonly diabetic, malnourished, or otherwise immunocompromised, infants in whom the disease develops are typically healthy and without clear predisposing factors. Herein, however, the authors report the case of an infant with compromised immunity secondary to the manifestations and treatment of panhypopituitarism, in whom postoperative necrotizing fasciitis developed after bilateral inguinal herniorrhaphy. The diagnosis, pathological mechanism, and treatment of necrotizing fasciitis are reviewed and the distinguishing features in infants are highlighted. The combination of a low incidence and very high mortality rate associated with necrotizing fasciitis in this subgroup strengthens the need for hypercritical suspicion. Early diagnosis and the prompt initiation of surgical treatment are the most essential means to improve on the prognosis for necrotizing fasciitis in infants.

Septic complications of hemorrhoidal banding.

Rubber band ligation is an efficacious and cost-effective alternative to conventional hemorrhoidectomy for symptomatic internal hemorrhoids. Even though the well-recognized complications of bleeding and thrombosis occur infrequently, far more serious septic complications have only recently been described, as evidenced in five of our patients: four cases were serious enough to necessitate surgical intervention, and one patient died. Pain followed by urinary dysfunction with or without toxic symptoms should alert the physician to the probability of localized perianal or systemic sepsis. Acute awareness of these rare but potentially life-threatening complications and immediate aggressive treatment is mandatory if death is to be prevented. Rubber band ligation of internal hemorrhoids need not be abandoned; however, the indications should be clear, the technique mastered, and a close patient follow-up maintained.

Presacral hematomas. Diagnosis and treatment.

A post-traumatic hematoma may present either acutely as a presacral collection or chronically as a retrorectal mass. A case of postpartum presacral hematoma and its management in the acute setting is described. A case of a chronic, calcified hematoma presenting as an asymptomatic retrorectal mass is also reported. CT scanning of the presacral space is the most accurate means of preoperative diagnosis. Therapy must be tailored to the preoperative diagnosis and to the size of the lesion.

Diverticulitis of the cecum and ascending colon.

Twelve cases of acute solitary diverticulitis of the cecum or ascending colon are reviewed. This is frequently indistinguishable from acute appendicitis preoperatively and is often mistaken for carcinoma at laparotomy. There are subtle clinical features that may help to suggest the diagnosis both before and during surgery. If diagnosed preoperatively, it can be treated effectively with broad spectrum antibiotics without surgical intervention. When diagnosed intraoperatively, hemicolectomy can often be avoided. Appendectomy should be done if resection is not performed.