Neonatal T4+ lymphocytes: analysis of the expression of 4B4 and 2H4 antigens

Bordetella pertussis infection in 2-month-old infants promotes type 1 T cell responses

Neonatal immaturity of the immune system is currently believed to generally limit the induction of immune responses to vaccine Ags and to skew them toward type 2 responses. We demonstrated here that Bordetella pertussis infection in very young infants (median, 2 mo old) as well as the first administration of whole-cell pertussis vaccine induces B. pertussis Ag-specific IFN-gamma secretion by the PBMC of these infants. IFN-gamma was secreted by both CD4(+) and CD8(+) T lymphocytes, and the levels of Ag-induced IFN-gamma secretion did not correlate with the age of the infants. Appearance of the specific Th-1 cell-mediated immunity was accompanied by a general shift of the cytokine secretion profile of these infants toward a stronger Th1 profile, as evidenced by the response to a polyclonal stimulation. We conclude that the immune system of 2-mo-old infants is developmentally mature enough to develop Th1 responses in vivo upon infection by B. pertussis or vaccination with whole-cell pertussis vaccines.

Adhesion of peripheral blood lymphocytes of children with arthritis to human umbilical vein endothelial cells

To determine whether adhesion of peripheral blood lymphocytes (PBL) of patients with juvenile rheumatoid arthritis (JRA) may be enhanced, adhesion of PBL of children with JRA, children with seronegative spondyloarthropathies (SSA), age-appropriate and adult controls, to human umbilical vein endothelial cells (HUVEC) was assessed in vitro. B and CD4 T lymphocytes in initial, adherent, and non-adherent cell fraction were identified by flow cytometry. B lymphocytes of all the younger subjects combined had a higher adherence to activated HUVEC compared with B lymphocytes of the adult donors. Except for greater adherence of HLA-DR+ CD4 T cells, lymphocytes of children with JRA showed no enhanced adhesion to either unactivated or activated HUVEC. The percentage of B cells adherent to activated HUVEC in each of the subject groups was 1.5-3.6-fold higher than adherent CD4 T lymphocytes. Surface analyses indicated higher percentages of CD49d (alpha 4)+ and CD29 (beta 1)+ CD4 T lymphocytes in adherent cells, but less of a differential in CD49 (alpha 4)+ and no difference in CD29 (beta 1)+ B lymphocytes. There were fewer Leu-8 (L-selectin)+ B and Leu-8+ CD4 T cells among adherent cells. The data suggest a greater adhesive capacity of B lymphocytes compared with CD4 T lymphocytes which is unrelated to disease, and the possibility that B lymphocytes may utilize adhesion molecules distinct from those of CD4 T lymphocytes. Only a small subset of T cells of patients with JRA may have an enhanced capacity for adhesion to endothelium.

Evolution of phenotypic memory T cells in HIV-1 infected infants and children

Infants are reported to be devoid of memory T cells at birth but acquired them with time. A cross-sectional study of peripheral blood mononuclear cells from HIV-infected and uninfected infants and children that bear the CD4R0 antigen was undertaken to describe the development of memory T cells. Linear regression lines derived from the data revealed increasing percentages of memory CD4 and CD8 cells in the uninfected children. Memory CD4 cells in the infected children were detected at a frequency equal to or greater than that seen in uninfected children until 6 months of age but subsequently declined with age. In contrast, memory CD8 cells were found to be significantly increased in HIV-infected children early in life with a rate of increase similar to that seen in the uninfected population. This increase in memory CD8 cells may facilitate the early diagnosis of HIV infection.

Immune responses during human schistosomiasis mansoni. XVIII. Immunologic status of pregnant women and their neonates

The immune status of peripheral blood mononuclear cells (PBMC) and sera of pregnant women infected with the helminth Schistosoma mansoni was studied during pregnancy and the cord blood mononuclear cells (CBMC) and sera from their offspring were studied at parturition. PBMC pokeweed mitogen-induced responses were maintained in gravid women, but the responses to both schistosome and non-schistosome antigenic preparations declined progressively during pregnancy. Schistosomal antigens stimulated proliferative responses by the CBMC of many neonates born of infected mothers, but not those of uninfected mothers. These specific responses by CBMC of only neonates born of infected mothers are indicative of in utero, cell-mediated sensitization of the neonates, which could be due either to circulating schistosomal antigens or to anti-idiotypic antibodies which cross the placenta during gestation. Sera from infected mothers and the cord blood sera from their babies showed the same levels of specific IgG anti-schistosomal activity. Anti-schistosomal IgM levels were maintained during pregnancy to some antigens and not to others, while such antibodies were rarely found in cord blood sera, and then only at very low levels.

Delineation of the functional capacity of human neonatal lymphocytes

Neonatal T cell-B cell collaboration was investigated utilizing a system of T cell-dependent polyclonal B cell activation and Ig secretion. In this system, T cells activated by immobilized anti-CD3 provide a potent stimulus for Ig production by adult lymphocytes. By contrast, anti-CD3 stimulation of cord blood lymphocytes generated minimal numbers of Ig-secreting cells. Ig production by neonatal lymphocytes was enhanced by the addition of Staphylococcus aureus or secreted factors from mitogen-stimulated adult T cells. Supplementation with IL-2 resulted in the production of large amounts of IgM and small amounts of IgG and IgA, with less Ig produced than by comparable cultures of adult lymphocytes. Neonatal T cells proliferated and produced IL-2 in response to immobilized anti-CD3, and supported B cell proliferation and Ig secretion by adult B cells, although not as effectively as adult T cells. Supernatants from activated neonatal T cells were markedly limited in their capacity to support Ig production by adult B cells. Neonatal B cells could be induced to differentiate in response to anti-CD3-stimulated adult T cells. However, the amounts of IgG and IgA secreted were small compared to adult levels. These studies indicate a relative, but not absolute, functional deficiency of both neonatal B and T cells.

Immunoglobulin and cytokine production by neonatal lymphocytes

Growth and differentiation of cord blood B cells were studied using T cell-depleted populations. In the absence of in vitro activation, cord blood B cells proliferated in response to cytokines including interleukin-2 (IL-2) and interleukin-4 (IL-4); anti-mu-stimulated cord B cells had a lesser response to IL-2 than adult cells. IgM synthesis by cord blood B cells was enhanced by interleukin-6 (IL-6) and decreased by IL-2. In cultures activated by Staphylococcus aureus Cowan I (SAC), cord blood B cells produced lesser increases in IgM than adult B cells regardless of the cytokine added. Cord blood B cells produced no IgG or IgA with any cytokine preparation with or without SAC activation. Supernatants of cord blood T cells pulse-stimulated with phytohaemagglutinin and phorbol myristate acetate contained less IL-2 and IL-6 and had less growth and differentiation activity than adult T cell supernatants. The results confirm a limited cord blood B cell response and also suggest a limitation in production of B cell stimulatory lymphokines by cord blood T cells.

Cellular and molecular mechanisms for reduced interleukin 4 and interferon-gamma production by neonatal T cells

The mechanisms by which T lymphocytes acquire the capacity to produce interleukin 4 (IL-4) and other lymphokines during intrathymic and extrathymic development are poorly understood. To gain insight into this process, we determined the capacity of human neonatal and adult T lineage cell populations to produce IL-4 after polyclonal activation. IL-2 and interferon-gamma (IFN-gamma) production were studied in parallel, since their production by neonatal T cells is known to be similar or diminished, respectively, compared to adult T cells. Production of IL-4 by neonatal CD4+ T cells and IFN-gamma by neonatal CD4+ and CD8+ T cells was markedly lower compared with analogous adult cell populations, whereas IL-2 production was similar. Transcription of IL-4, as determined by nuclear run-on assays, and IL-4 mRNA-containing cells, as determined by in situ hybridization, were undetectable in neonatal T cells, whereas both were detectable in adult T cells. IFN-gamma transcription and IFN-gamma mRNA-containing cells were reduced in neonatal T cells compared with adult T cells. Reduced lymphokine production by neonatal T cells correlated with their lack of a CD45R- (putative memory T cell) population; cells with this surface phenotype comprised 30-40% of the adult CD4+ T cells and were highly enriched for IL-4 and IFN-gamma, but not IL-2 production. IL-4, IFN-gamma, and IL-2 mRNA expression by neonatal CD4+CD8- thymocytes was similar to that found in circulating neonatal CD4+ T cells. Taken together, these findings suggest that the extrathymic generation of memory T cells during postnatal life may result in an increased capacity for IL-4 and IFN-gamma gene expression. In addition, IFN-gamma and IL-2 mRNA were significantly more abundant than IL-4 mRNA in activated neonatal CD4+CD8- thymocytes and CD4+ T cells, as well as adult CD4+ CD45R- T cells. Therefore, the capacity of T lineage cells to express the IL-4 gene may be more restricted compared to other lymphokine genes beginning in intrathymic development. This restricted capacity appears to persist during postnatal extrathymic maturation of T cells.