This study addresses the relative importance of CD134 (OX40) and CD137 (4‐1BB) in the costimulation of CD4+ and CD8+ T cells under comparable conditions of antigenic stimulation. We demonstrate that CD134 is capable of directly costimulating CD8+ T cells. However, costimulation of CD8+ T cells by CD134 is less potent than that triggered by CD137. The higher costimulatory activity of CD137, when compared with CD134, correlates well with its faster expression kinetics and higher levels on CD8+ T cells. Furthermore, induction of CD137 expression on CD8+ T cells is highly sensitive to low levels of TCR stimulation, which is in contrast with CD134. Conversely, CD134 is more effective than CD137 in costimulating CD4+ T cells. This, however, could not be attributed to differential expression. We also demonstrate that the transient nature of CD134 and CD137 expression on activated CD4+ T cells is the resultof proteolytic shedding. Consistent with the greater ability of CD137 to costimulate CD8+ T cells, stimulation of CD137 in vivo is considerably more effective than CD134 in augmenting anti‐tumor immune responses. Therefore, agents that stimulate signaling via CD137 are likely to be more useful in clinical conditions where highly effective CD8+ CTL responses are required.
The delayed presentation of traumatic diaphragmatic hernia is associated with high morbidity and mortality. Acute colobronchial fistula complicating delayed presentation of traumatic diaphragmatic hernia is previously unreported. A 52-year-old woman presented with a 4-day history of dyspnoea, feculent sputum and chest and abdominal pain 3 months after a road traffic accident. The diagnosis of Chilaiditi's syndrome, diaphragmatic hernia and colobronchial fistula was confirmed with computed tomography (CT) and treated by chest drain, primary hernia repair and right hemicolectomy. Spontaneous decompression through the bronchus had prevented tension fecopneumathorax. The diagnosis of diaphragmatic hernia is difficult but delay is associated with increased mortality. Symptoms include dyspnoea, chest and abdominal pain, with decreased respiratory sounds and visceral sounds in the thorax. Abdominal visceral structures or gas on CXR, CT or contrast studies will confirm the diagnosis. The initial operative approach is laparotomy but thoracotomy must be considered as abdominal viscera may be adherent to thoracic structures.
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