CD69, an 'activation marker' that is rapidly induced on mature T cells after stimulation through the T cell antigen receptor (TCR) was found to be expressed on approximately 10% of normal thymocytes. All of these CD69+ thymocytes express alpha beta TCR, and they include both TCRlowCD4+CD8+ and TCRhighCD4+CD8- or CD4-CD8+ thymocytes. The CD69+ cells can be further segregated into heat-stable antigen (HSA)+TCRlow, HSA+TCRhigh and HSA-TCRhigh thymocyte populations. None of CD69+ cells express the mature T cell marker Qa-2. Thus CD69+ cells present in vivo appear phenotypically to represent transitional cell populations between immature TCRlowHSA+Qa-2-double-positive cells and mature TCRhighHSA-QA-2+ single-positive cells. In addition, TCR engagement by MHC molecules is required for CD69 expression in the thymus. Taken together, the CD69+ thymocytes appear to represent the cells auditioning in positive selection process or they are the cells that have been positively selected recently. Analysis of a TCR transgenic mouse model revealed an increased number of CD69+ thymocytes in a positively selecting thymus, whereas no CD69+ transgenic TCR+ thymocytes were observed in the non-selecting thymus. Based on the results of this study, we suggest that the surface expression of CD69 serves as a useful marker to identify and trace those thymocytes that are engaged in the TCR-mediated positive selection process in the thymus.

The results suggest the usefulness of 5-HT(1A) agonists for enhancing some types of cognitive performance and possibly social and work function in patients with schizophrenia.

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Brain abnormalities of schizophrenia probably consist of deviation related to the vulnerability and pathological changes in association with overt psychosis. We conducted a cross-sectional comparison in brain morphology between patients with overt schizophrenia and schizotypal disorder, a schizophrenia-spectrum disorder without florid psychotic episode. Voxelbased morphometry was applied to assess gray matter volume in 25 patients with schizophrenia, 25 patients with schizotypal disorder, and 50 healthy control subjects. In comparison with controls, schizophrenia patients showed gray matter reductions in the bilateral medial frontal, inferior frontal, medial temporal, and septal regions, and the left middle frontal, orbitofrontal, insula, and superior temporal regions, and an increased gray matter in the left basal ganglia. Schizotypal disorder patients showed reductions in the left inferior frontal, insula, superior temporal, and medial temporal regions. There was a significant reduction in the left orbitofrontal region of schizophrenia compared with schizotypal disorder. Gray matter reductions that are common to both patient groups such as those in the left medial temporal and inferior frontal regions may represent vulnerability to schizophrenia, and additional involvement of several frontal regions may be crucial to florid psychosis.