B cell subsets in thymus from infants with Down syndrome

ABSTRACT: B lymphocytes are still poorly characterized in the human thymus, and due to the immunological peculiarities of Down syndrome, a detailed investigation of thymic B lymphocytes and their subsets was performed in <2-year-old infants. This is a period of intense thymic activity, and here we compared thymuses from infants with Down syndrome (DG) and age-matched control group (CG) with heart disease as the only described malformation, no clinical signs of immunodeficiency and normal blood lymphocyte numbers. METHODS: This study, approved by the institutional ethics committee, included 10 thymic samples from DG infants, and 20 from CG infants. Depending on thymus size and the type of surgical approach, babies were submitted to total thymectomy or only the removal of a small thymic fragment (mainly in the DG), always during cardiac surgery in order to correct congenital defects. Flow cytometry was used for immunophenotyping of cell suspension obtained from thymic tissue; and the B lymphocyte topographic localization was investigated by immunohistochemistry, and a quantitative evaluation of B-cells in each region was carried out using methods of digitized images analysis. RESULTS: Flow cytometry revealed that CD20+ cells represent around 1% of total lymphocytes in both groups, with higher naive and lower unswitched memory B lymphocyte frequencies in DG when compared to the CG, while B1 cells were present in much higher frequency in DG than in CG. All the other B-cell subpopulations (transitional, switched memory, plasmablasts and plasmocytes) were statistically equivalent between groups. Immunohistochemistry showed higher frequencies of CD20+ cells in medullary region compared to cortex, without differences between the groups (DG = 16.8% and CG = 17.1% of total cell number), while the cortex region had few B cells in both groups, with significantly lower frequency in DG group, reaching 0.25%, compared with the CG, which showed 0.6%. CONCLUSION: Flow cytometry revealed a different distribution of B-cell subtypes in DG thymus compared to CG and, thus, data obtained from such rare material could be relevant in the characterization and further analysis and understanding of the immunological mechanisms that involve the participation of B lymphocyte subpopulations in the thymus. FAPESP (grant 2014/50489-9).

Neonatal infection and passive acquisition of serum total IgG and reactive with Streptococcus B, anti-LPS of Klebsiella spp and Pseudomonas spp antibodies in twins

SUMMARY OBJECTIVE To describe the concentration of total and specific IgG antibodies anti-Streptococcus B, anti-lipopolysaccharide of Klebsiella spp, and anti-lipopolysaccharide of Pseudomonas spp in the umbilical cord of newborn(NB) twins and to analyze the association between neonatal infection and antibody concentration in the umbilical cord blood. METHODS A prospective cross-sectional study of a cohort of NB twins admitted during the period of 20 months. Patients with malformations and mothers with infection were excluded. Variables analyzed: gestational age(GA); birth weight(BW); antibody concentrations in umbilical cord blood; infection episodes. We used the paired Student t-test, Spearman correlation, and generalized estimation equation. RESULTS 57 pairs of twins were included, 4 excluded, making the sample of 110 newborns. GA=36±1.65weeks and BW=2304.8±460g(mean±SD). Antibody concentrations in twins(mean±SD): total IgG=835.71±190.73mg/dL, anti-StreptococcusB IgG=250.66±295.1 AU/mL, anti-lipopolysaccharide of Pseudomonas spp IgG=280.04±498.66 AU/mL and anti-lipopolysaccharide of Klebsiella spp IgG=504.75±933.93 AU/mL. There was a positive correlation between maternal antibody levels and those observed in newborns(p <0.005). The transplacental transfer of maternal total IgG and anti-LPS Pseudomonas IgG antibodies was significantly lower at NB GA <34 weeks(p <0.05). Five newborns were diagnosed with an infection. Infants with infection had significantly lower total IgG concentration(p <0.05). CONCLUSION This study showed a positive correlation between maternal and newborn antibodies levels. In infants younger than 34 weeks there is less transfer of total IgG and anti-LPS Pseudomonas IgG. The highest incidence of infection in the newborn group who had significantly lower total IgG serum antibodies reinforces the importance of anti-infectious protection afforded by passive immunity transferred from the mother.

RESUMO OBJETIVOS Descrever o título de anticorpos IgG total e específico anti-Streptococcus B, anti-lipopolissacarídeos(LPS) de Klebsiella e Pseudomonas no cordão umbilical em gêmeos e analisar a possível associação entre os títulos desses anticorpos e a ocorrência de infecção. MÉTODOS Estudo prospectivo transversal de uma coorte de recém-nascidos (RN) gemelares em 20 meses. Excluídos: malformação, infecção congênita ou materna. Variáveis estudadas: idade gestacional(IG); peso de nascimento(PN); título de anticorpos e episódios de infecção. Foram utilizados testes t-Student pareado, correlação de Spearman e equações de estimação generalizadas. RESULTADOS Elegíveis 59 pares de gêmeos, excluídos 4 e incluídos 55 pares (n=110RN). A IG foi 36±1,65semanas e o PN foi 2304,8±460g (média±DP). Concentrações de anticorpos dos RN(média±DP): IgG total=835,71±190,73 mg/dL, IgG anti-Streptococcus B=295,1±250,66 UA/mL, IgG anti-LPS Pseudomonas=280,04±498,66 UA/mL e IgG anti-LPS Klebsiella=504,75± 933,93UA/mL. Houve correlação positiva entre níveis de anticorpos maternos e aqueles observados nos RN (p<0,005). A transferência transplacentária de anticorpos maternos IgG total e IgG anti-LPS Pseudomonas foi significativamente menor em RN IG < 34semanas (p<0,05). Foram diagnosticados 5 RN com infecção. Os RN que apresentaram infecção tinham concentração de IgG total significativamente menor (p<0,05). CONCLUSÕES Na população estudada existe correlação entre os anticorpos maternos e os níveis de anticorpos no RN. Nos gêmeos menores que 34 semanas há menor transferência de IgG total e IgG anti-LPS Pseudomonas. Nos RN com infecção a concentração de IgG total é significativamente menor, o que demonstra a maior vulnerabilidade e risco de infecção dessa população e a importância da imunidade passiva transferida pela placenta.

Placental and colostral transfer of antibodies reactive with enteropathogenic Escherichia coli intimins a, ß, or gama / Transferência placentária e colostral de anticorpos reativos a Escherichia coli enteropatogênica com expressão das intiminas a, ß ou gama

Intimins are protein adhesins of enteropathogenic Escherichia coli and enterohemorrhagic E. coli capable of inducing attachment and effacement lesions in enterocytes. Anti-intimin antibodies are important for the protection from enteropathogenic E. coli and enterohemorrhagic E. coli infections because these antibodies inhibit bacterial adhesion and impair the initial step of the pathogenesis. We studied the transfer of maternal anti-intimin antibodies from healthy Brazilian mothers to their newborns through the placenta and colostrum. Methods Serum immunoglobulin G and secretory immunoglobulin A antibodies against conserved and variable regions of intimins a, ß, and gama were analyzed using an enzyme linked-immunosorbent assay in the blood and colostrum from 45 healthy women as well as cord blood serum samples from their newborns. Results The concentrations of antibodies reactive with a intimin were significantly lower than those of anti-gama and anti-conserved intimin antibodies in the colostrum samples. IgG serum antibodies reactive with all the subtypes of intimins were transferred to the newborns, but the concentrations of anti-conserved intimin serum antibodies were significantly higher in mothers and newborns than concentrations of antibodies against variable regions. The patterns of IgG transfer from mothers to newborns were similar for all anti-intimin antibodies. These values are similar to the percentage transference of total IgG. Conclusions Anti-intimin antibodies are transferred from mothers to newborns through the placenta, and reinforce the protection provided by breastfeeding against diarrheagenic E. coli infections.

Objetivo As Intiminas são adesinas proteicas de Escherichia coli enteropatogênicas e enterohemorrágicas capazes de induzir as lesões "attaching and effacing" nos enterócitos. Anticorpos anti-intiminas são importantes para a proteção contra infecções por E. coli enteropatogênica e E. coli enterohemorrágica porque estes anticorpos inibem a adesão bacteriana impedindo o passo inicial do mecanismo patogênico destas bactérias. Nós estudamos a transferência de anticorpos maternos anti-intiminas de mães brasileiras saudáveis para os seus recém-nascidos através da placenta e do colostro. Métodos Anticorpos séricos da classe IgG e secretórios da classe IgA reativos com as porções conservada e variáveis das intiminas a, ß e gama foram analisados pelo teste imunoenzimático no sangue e no colostro de 45 parturientes saudáveis e no sangue de cordão umbilical dos seus respectivos recém-nascidos. Resultados As concentrações de anticorpos reativos com intimina va foram significativamente mais baixas que as dos anticorpos anti-gama e anti-intimina conservada nas amostras de colostro. Anticorpos IgG séricos reativos com todas as intiminas foram transferidos para os recém-nascidos, mas as concentrações de anti-intimina conservada foram significativamente mais altas tanto nas mães como nos recém-nascidos do que os anticorpos reativos com as regiões variáveis das intiminas. O padrão de transferência de IgG das mães para os recém-nascidos foi muito semelhante para todos os anticorpos anti-intiminas. Os valores de porcentagem de transferência foram semelhantes à transferência de IgG total. Conclusões Anticorpos anti-intimina são transferidos das mães para os recém-nascidos pela placenta e corroboram a proteção contra infecções por Escherichia coli diarreiogênicas conferida pelo aleitamento materno.