Inhibitory receptor expression on neonatal immune cells

Neonates are born with quantitative and qualitative defects in both adaptive and innate immune responses. The immune system is regulated by several mechanisms, including the signalling of inhibitory receptors. Increased expression of inhibitory receptors may result in a higher threshold for activation and suppressed function of neonatal cells. The aim of this study was to determine whether the expression of seven inhibitory receptors is increased on neonatal immune cells compared to adult immune cells. In a healthy birth cohort, we examined the expression of seven inhibitory immune receptors on neonatal neutrophils, monocytes, natural killer (NK) cells, CD4(+) and CD8(+)T cells. The expression of leucocyte-associated immunoglobulin (Ig)-like receptor-1 (LAIR-1), signal inhibitory receptor on leucocytes-1 (SIRL-1), CD31, signal-regulatory protein alpha (SIRPα), Siglec-9, CD200R, immune receptor expressed on myeloid cells-1 (IREM-1) and the membrane-bound ligand CD200 was studied by flow cytometry on leucocytes in cord blood (n = 14), neonatal venous blood (n = 24) and adult venous blood (n = 22). Expression of LAIR-1, CD31 and CD200 was increased consistently across all neonatal T cell subsets. Neonatal monocytes exhibited decreased expression of LAIR-1 and IREM-1 compared to adults. Furthermore, cord blood and neonatal venous blood samples contained a distinct LAIR-1-positive neutrophil population, which was not detected in adult blood. We demonstrated distinct expression of inhibitory receptors on neonatal peripheral blood immune cells in a healthy birth cohort. This is the first evidence that inhibitory receptors play a role in regulation of the neonatal immune system. Consistently increased inhibitory receptor expression on T cells may be an important mechanism in preventing the development of allergy and autoimmunity.

Selection of probiotic bacteria for prevention of allergic diseases: immunomodulation of neonatal dendritic cells

Modification of intestinal microbiota early in life by administration of probiotic bacteria may be a potential approach to prevent allergic disease. To select probiotic bacteria for in vivo purposes, we investigated the capacity of probiotic bacteria to interact with neonatal dendritic cells (DC) and studied the ensuing T cell polarizing effect. Immature DC were generated from cord blood-derived monocytes and maturation was induced by maturation factors (MF), lipopolysaccharide (LPS) plus MF and Bifidobacterium bifidum, B. infantis, Lactobacillus salivarius, Lactococcus lactis alone or combined with MF. After 12 days of co-culture with DC and Staphylococcus aureus enterotoxin B (SEB) as antigenic stimulus, cytokine production by autologous T cells was determined by intracellular cytokine staining. Additionally, cells were stimulated with CD3 and CD28 monoclonal antibodies and cytokines were measured in supernatants by multiplex assay. The probiotic strains induced partial maturation of DC. Full maturation of DC was induced for all strains tested when MF was added. The percentage of interleukin (IL)-4 producing T cells was lower in T cell cultures stimulated with B. bifidum matured DC compared to MF and LPS matured DC, which coincided with a higher percentage of interferon (IFN)-gamma-producing T cells. Furthermore, T cells stimulated by B. bifidum matured DC produced significantly more IL-10 compared to MF matured DC. Selected species of the Bifidobacterium genus prime in vitro cultured neonatal DC to polarize T cell responses and may therefore be candidates to use in primary prevention of allergic diseases.

Selection of probiotic bacteria for prevention of allergic diseases: immunomodulation of neonatal dendritic cells

Modification of intestinal microbiota early in life by administration of probiotic bacteria may be a potential approach to prevent allergic disease. To select probiotic bacteria for in vivo purposes, we investigated the capacity of probiotic bacteria to interact with neonatal dendritic cells (DC) and studied the ensuing T cell polarizing effect. Immature DC were generated from cord blood-derived monocytes and maturation was induced by maturation factors (MF), lipopolysaccharide (LPS) plus MF and Bifidobacterium bifidum, B. infantis, Lactobacillus salivarius, Lactococcus lactis alone or combined with MF. After 12 days of co-culture with DC and Staphylococcus aureus enterotoxin B (SEB) as antigenic stimulus, cytokine production by autologous T cells was determined by intracellular cytokine staining. Additionally, cells were stimulated with CD3 and CD28 monoclonal antibodies and cytokines were measured in supernatants by multiplex assay. The probiotic strains induced partial maturation of DC. Full maturation of DC was induced for all strains tested when MF was added. The percentage of interleukin (IL)-4 producing T cells was lower in T cell cultures stimulated with B. bifidum matured DC compared to MF and LPS matured DC, which coincided with a higher percentage of interferon (IFN)-gamma-producing T cells. Furthermore, T cells stimulated by B. bifidum matured DC produced significantly more IL-10 compared to MF matured DC. Selected species of the Bifidobacterium genus prime in vitro cultured neonatal DC to polarize T cell responses and may therefore be candidates to use in primary prevention of allergic diseases.