The thymus is a primary lymphoid organ responsible for the maturation of T cells as well as the immunological central tolerance. It is in the antenatal period and infancy that it plays its major role. In clinical practice, T cell receptor excision circles (TRECs) are considered a direct and reliable measure of the thymic function. TRECs are a by-product of DNA formation in gene rearrangement of T cell receptors. They are stable and they do not duplicate during mitosis, representing the recent emigrant T cells from the thymus. Despite their importance, TRECs have been neglected by physicians and there is a lack of data regarding thymic function during infancy of healthy children. In order to evaluate thymic function in the first years of life, we propose measuring TRECs as a valuable tool. One hundred and three blood samples from children and adolescents between 3 months and 20 years of age were analyzed. The mean TRECs count was 136.77±96.7 copies of TRECs/μL of DNA. The individuals between 0 and 5 years of age had significantly higher TRECs values than those between 10 and 20 years of age. No significant difference was observed in TRECs values among age groups below 5 years of age. An inverse correlation between TRECs and age was found (r=0.3 P=0.003). These data highlight and validate the evidence of decreased thymus function with age, even during infancy. Awareness should be raised with this important albeit ignored organ.

Rubinstein-Taybi syndrome (RTS) is a rare developmental disorder characterized by craniofacial dysmorphisms, broad thumbs and toes, mental and growth deficiency, and recurrent respiratory infections. RTS has been associated with CREBBP gene mutations, but EP300 gene mutations have recently been reported in 6 individuals. In the present study, the humoral immune response in 16 RTS patients with recurrent respiratory infections of possible bacterial etiology was evaluated. No significant differences between patients and 16 healthy controls were detected to explain the high susceptibility to respiratory infections: normal or elevated serum immunoglobulin levels, normal salivary IgA levels, and a good antibody response to both polysaccharide and protein antigens were observed. However, most patients presented high serum IgM levels, a high number of total B cell and B subsets, and also high percentiles of apoptosis, suggesting that they could present B dysregulation. The CREBBP/p300 family gene is extremely important for B-cell regulation, and RTS may represent an interesting human model for studying the molecular mechanisms involved in B-cell development.

RESUMO A ocorrência da mosca-branca Bemisia tabaci (Genn.) biótipo B (Hemiptera: Aleyrodidae) foi registrada pela primeira vez em mudas de Eucalyptus camaldulensis Dehn. em Lavras, Estado de Minas Gerais. O ataque foi observado no dia 16/1/2007 em 30 mudas de E. camaldulensis mantidas em casa-de-vegetação. As plantas infestadas apresentavam-se amarelecidas e em estágio inicial de definhamento como resposta ao ataque do inseto.

ABSTRACT The occurrence of Bemisia tabaci (Genn.) biotype B (Hemiptera: Aleyrodidae) is record for the first time in Eucalyptus camaldulensis Dehn. seedlings in Lavras, State of Minas Gerais, Brazil. The attack was seen on 16/1/2007 at 30 seedlings of E. camaldulensis kept in greenhouse. The infested plants were yellowish and in initial stage of weakening as response to the attack of the insect.

This study verified the host species of the parasitoid Hemencyrtus herbertii Ashmead (Hymenoptera: Encyrtidae), in Lavras, Minas Gerais, Brazil. The pupae were obtained by the flotation method. They were individually placed in gelatin capsules until the emergence of adult flies or their parasitoids. The overall occurence of parasitism was 6.5%. The occurrence of parasitism presented in the hosts Chrysomya megacephala (Diptera: Calliphoridae) and Sarcodexia lambens (Diptera: Sarcophagidae) was 1.3% and 29.4%, respectively.