Selection of Thymocytes Expressing Transgenic TCR Specific for a Minor Histocompatibility Antigen, H60

Minor histocompatibility antigens are MHC-bound peptides and contribute to the generation of allo-responses after allogeneic transplantation. H60 is a dominant minor H antigen that induces a strong CD8 T-cell response in MHC-matched allogeneic transplantation settings. Here, we report establishment of a TCR transgenic mouse line named J15, wherein T cells express TCRs specific for H60 in complex with H-2K(b), and different fates of the thymocytes expressing J15 TCRs in various thymic antigenic environments. Thymocytes expressing the J15 TCRs were positively selected and differentiated into CD8+ single positive (SP) cells in the thymus of C57BL/6 mice, wherein the cognate antigen H60 is not expressed. However, thymocytes were negatively selected in thymus tissue where H60 was transgenically expressed under the control of the actin promoter, with double-positive stages of cells being deleted. Despite the ability of the H60H peptide (LTFHYRNL) variant to induce cytotoxic activity from H60-specific CTL lines at ~50% of the activity induced by normal H60 peptides (LTFNYRNL), J15-expressing thymocytes were positively selected in the thymus where the variant H60H was transgenically expressed. These results demonstrate that a single amino-acid change in the H60 epitope peptide influences the fate of thymocytes expressing the cognate TCR.

Subdominant H60 antigen-specific CD8 T-cell response precedes dominant H4 antigen-specific response during the initial phase of allogenic skin graft rejection

In allogeneic transplantation, including the B6 anti-BALB.B settings, H60 and H4 are two representative dominant minor histocompatibility antigens that induce strong CD8 T-cell responses. With different distribution patterns, H60 expression is restricted to hematopoietic cells, whereas H4 is ubiquitously expressed. H60-specific CD8 T-cell response has been known to be dominant in most cases of B6 anti-BALB.B allo-responses, except in the case of skin transplantation. To understand the mechanism underlying the subdominance of H60 during allogeneic skin transplantation, we investigated the dynamics of the H60-specific CD8 T cells in B6 mice transplanted with allogeneic BALB.B tail skin. Unexpectedly, longitudinal bioluminescence imaging and flow cytometric analyses revealed that H60-specific CD8 T cells were not always subdominant to H4-specific cells but instead showed a brief dominance before the H4 response became predominant. H60-specific CD8 T cells could expand in the draining lymph node and migrate to the BALB.B allografts, indicating their active participation in the anti-BALB.B allo-response. Enhancing the frequencies of H60-reactive CD8 T cells prior to skin transplantation reversed the immune hierarchy between H60 and H4. Additionally, H60 became predominant when antigen presentation was limited to the direct pathway. However, when antigen presentation was restricted to the indirect pathway, the expansion of H60-specific CD8 T cells was limited, whereas H4-specific CD8 T cells expanded significantly, suggesting that the temporary immunodominance and eventual subdominance of H60 could be due to their reliance on the direct antigen presentation pathway. These results enhance our understanding of the immunodominance phenomenon following allogeneic tissue transplantation.

Requirement of CD4 Help for Induction of CD8 T Cell Response Specific for Virally Derived H60

CD40-CD40L-mediated help from CD4 T cells is essential to induce primary CD8 T cell responses specific to the non-inflammatory cell-based antigen H60. In this study, using H60 as a model antigen, we generated recombinant vaccinia viruses (rVVs) expressing the H60 CD8 epitope and investigated whether CD4 help was required to activate the CD8 T cell response specific to the virally expressed H60. The immune response after infection with rVVs expressing H60 was similar to that after immunization with H60 congenic splenocytes, with a peak frequency of H60-specific CD8 T cells detected in the blood on day 10 post-infection. A CD8 T cell response specific for virally derived H60 was not induced in CD4-depleted mice, but was in CD40-deficient mice. These results provide insights into the characterization of the CD8 T cell response specifically for antigens originating from cellular sources compared to viral sources.

Intravitreal Bevacizumab for Treatment of Macular Edema Secondary to Hemicentral Retinal Venous Occlusion and Concentrations of Cytokine in Aqueous Humor

PURPOSE: To evaluate the effects of intravitreal bevacizumab and to investigate the concentrations of cytokine in the aqueous humors of patients with macular edema secondary to hemicentral retinal venous occlusion. METHODS: Fifteen eyes of 15 patients with macular edema secondary to hemicentral retinal venous occlusion received intravitreal bevacizumab injections and completed 12 months of follow-up. Cytokine levels were measured in the aqueous humors of these patients using a multiplex bead assay and the levels were compared with those of the controls. RESULTS: During 12 months of follow-up, a mean of 4.5 intravitreal bevacizumab injections were performed. The visual acuity and the central macular thickness improved significantly (p = 0.028, p = 0.000) after treatment. The levels of interleukin-6, vascular endothelial growth factor, and monocyte chemoattractant protein-1 were increased in the aqueous humor compared with the levels in the control group (p = 0.010, p = 0.045, p < 0.001). CONCLUSIONS: Elevated cytokine levels were identified in the aqueous humor after hemicentral retinal venous occlusion. Intravitreal bevacizumab injections were effective for improvements in visual acuity and macular edema due to hemicentral retinal venous occlusion.

The Effect of Intravitreal Bevacizumab in Patients with Acute Central Serous Chorioretinopathy

PURPOSE: To evaluate the effect of intravitreal bevacizumab injection (IVBI) in acute central serous chorioretinopathy (CSC) patients. METHODS: Patients with acute CSC received IVBI (1.25 mg/0.05 mL) or observation by randomization. Twelve eyes in each group completed 6 months of regular follow-up and were ultimately included in this study. Each patient was assessed using best corrected visual acuity measurements, fluorescein angiography, and optical coherence tomography at baseline and had regular follow-ups after treatment. RESULTS: All patients showed improvements in visual acuity and fluorescein angiographic leakage and had resolution of their neurosensory detachment following treatment. There were no significant differences in visual acuity, central retinal thickness, or remission duration between the IVBI group and the control group at baseline or after treatment (p>0.05). CONCLUSIONS: Intravitreal bevacizumab showed no positive effect in acute CSC patients compared to the observation group, and there were no adverse effects of treatment. Further investigation will be helpful to understand this therapy in patients with CSC.

A Case of Micturition Syncope in a Child

Syncope in children and adolescents have a common occurrence according for up to 15% before adulthood. Micturition syncope, a kind of situational syncope, can be considered a form of reflex syncope. It can typically occur in healthy young men after rising from bed in the early morning who experience sudden loss of consciousness during or immediately after urination. The mechanism of micturition syncope is not completely understood, but it has been suggested that vasovagal reflex mediated bradycardia and peripheral vasodilation and decreased venous return due to Valsalva effect and standing position lead to the decrease in cerebral blood flow resulting in syncope. The causes of syncope are variable. So complete history taking, physical examination, electrocardiography, exercise stress test, echocardiography, head-up tilt table test, electroencephalography(EEG), brain magnetic resonance image and urodynamic study should be required for the diagnosis of micturition syncope. There were several reports about micturition syncope. However, literature of micturition syncope at the pediatric age has rarely been reported in Korea so far. Therefore, we report a case of a 9- year-old boy with micturition syncope with typical EEG findings of high amplitude delta wave and flattening during syncope.

Role of Transesophageal Pacing in Evaluation of Palpitation in Infants and Children

PURPOSE: We intended to find out the role of transesophageal atrial pacing in evaluation of infants and children with palpitation of unknown origin. METHODS: We tried transesophageal atrial pacing study in 69 infants and children with palpitation, in whom tachycardia wasn't documented in electrocardiogram and reviewed retrospectively the records of transesophageal pacing and medical records of theses patients to find out the induction rate of tachycardia by transesophageal atrial pacing and the possible mechanism of tachycardia if induced. RESULTS: In 70.1% infants and children with palpitation, tachycardia was induced, so we could conclude that tachycaridia was the cause of palpitation in these cases. In most cases, tachycardia was induced by rapid atrial pacing, and in 21% by using isoproterenol. Tachycardia induction rate was higher in or =6-year-old children(P<0.05). In cases of the induced, we reviewed the mechanism of tachycardia. Of these induced tachycardias, 53.2% is atrioventricular reentry tachycardia, 34.0% were atrioventricular nodal reentry tachycardia, and 12.8% were idiopathic left ventricular tachycardia. Invasive electrophysiologic study was done to 10 patients of those induced. The results of electrophysiologic study and transesophageal pacing and recording were the same except for one patient. CONCLUSION: Transesophageal atrial pacing and recording is a less invasive, safe and useful method to find out the cause of palpitation and the mechanism of tachycardia in infants and children.