Circulating pathogen-specific plasmablasts in female patients with upper genital tract infection

Mucosal antibodies constitute the first line of adaptive immune defence against invaders in the female genital tract (FGT), yet the sequence of events leading to their production is surprisingly poorly characterized. We explored the induction of pathogen-specific antibody-secreting cells (ASC) as a response to an acute infection in the upper FGT. We recruited 12 patients undergoing surgery due to an upper FGT infection (7/12 blood culture positive, 5/ 12 negative) and six healthy controls. Pathogens were sampled during surgery and PBMC collected in the acute phase of the disease (days 7-10). We searched by ELISPOT circulating pathogen-specific ASC and explored their frequency, immunoglobulin isotype distribution, and expressions of homing receptors (alpha(4)beta(7), L-selectin, and CLA). All patients had circulating ASC specific to the infective bacteria; the geometric mean was 434 (95%CI 155-1234) ASC (IgA + IgG + IgM)/10(6) PBMC. IgA ASC predominated in 7/12, IgG ASC in 3/12, and IgM ASC in 2/12 cases. Of all the pathogen-specific ASC, 60% expressed alpha(4)beta(7), 67% L-selectin, and 9% CLA. This study is the first to show induction of pathogen-specific ASC in the peripheral blood in bacterial infection in the human FGT. Our findings reveal that such FGT-originating pathogen-specific ASC are predominated by IgA ASC and exhibit a homing receptor profile resembling that of ASC in acute urinary tract infection. The data thus suggest a characteristic profile shared by the urogenital tract.Peer reviewe

Immune Defense in Upper Airways : A Single-Cell Study of Pathogen-Specific Plasmablasts and Their Migratory Potentials in Acute Sinusitis and Tonsillitis

Background Despite the high frequency of upper respiratory tract (URT) infections and use of the nasal mucosa as route for vaccination, the local immune mechanism and dissemination of effector lymphocytes from the URT have been insufficiently characterized. To devise a single-cell approach for studying the mucosal immune response in the URT, we explored URT-originating B effector lymphocytes in the circulation of patients with one of two common respiratory infections, acute sinusitis or tonsillitis. Methods Patients with acute sinusitis (n = 13) or tonsillitis (n = 11) were investigated by ELISPOT for circulating pathogen-specific antibody-secreting cells (ASCs) of IgA, IgG and IgM isotypes approximately one week after the onset of symptoms. These cells' potential to home into tissues was explored by assessing their expression of tissue-specific homing receptors alpha(4)beta(7), L-selectin, and cutaneous lymphocyte antigen (CLA). Results Pathogen-specific ASCs were detected in the circulation of all patients, with a geometric mean of 115 (95% CI 46-282) /10(6) PBMC in sinusitis, and 48 (27-88) in tonsillitis. These responses were mainly dominated by IgG. In sinusitis alpha(4)beta(7) integrin was expressed by 24% of the ASCs, L-selectin by 82%, and CLA by 21%. The proportions for tonsillitis were 15%, 80%, and 23%, respectively. Healthy individuals had no ASCs. Conclusions URT infections-acute sinusitis and tonsillitis-both elicited a response of circulating pathogen-specific plasmablasts. The magnitude of the response was greater in sinusitis than tonsillitis, but the homing receptor profiles were similar. Human nasopharynx-associated lymphoid structures were found to disseminate immune effector cells with a distinct homing profile.Peer reviewe

Pathogen-Specific Circulating Plasmablasts in Patients with Pneumonia

Peer reviewe

Differences in Homing Potentials of Streptococcus pneumoniae-Specific Plasmablasts in Pneumococcal Pneumonia and After Pneumococcal Polysaccharide and Pneumococcal Conjugate Vaccinations

Background. Mucosal immune mechanisms in the upper and lower respiratory tracts may serve a critical role in preventing pneumonia due to Streptococcus pneumoniae. Streptococcus pneumoniae-specific plasmablasts presumably originating in the lower respiratory tract have recently been found in the circulation in patients with pneumonia. The localization of an immune response can be evaluated by exploring homing receptors on such plasmablasts, yet no data have thus far described homing receptors in pneumonia. Methods. The expression of alpha(4)beta(7), L-selectin, and cutaneous lymphocyte antigen (CLA) on S. pneumoniae-specific plasmablasts was examined in patients with pneumonia (n = 16) and healthy volunteers given pneumococcal polysaccharide vaccine (PPV; n = 14) or pneumococcal conjugate vaccine (PCV; n = 11). Results. In patients with pneumonia, the proportion of S. pneumoniae-specific plasmablasts expressing L-selectin was high, the proportion expressing alpha(4)beta(7) was moderate, and the proportion expressing CLA was low. The homing receptor alpha(4)beta(7) was expressed more frequently in the pneumonia group than in the PPV (P=.000) and PCV (P=.029) groups, L-selectin was expressed more frequently in the PPV group than in the PCV group (P=.014); and CLA was expressed more frequently in the pneumonia group than in the PPV group (P=.001). Conclusions. The homing receptor profile in patients with pneumonia was unique yet it was closer to that in PCV recipients than in PPV recipients. These data suggest greater mucosal localization for immune response in natural infection, which is clinically interesting, especially considering the shortcomings of vaccines in protecting against noninvasive pneumonia.Peer reviewe

Plasmablast response in pneumococcal pneumonia.

<p>Numbers of pathogen-specific plasmablasts identified as antibody-secreting cells/10⁶ PBMC in IgA-, IgG- and IgM-isotypes in 16 patients with acute <i>Streptococcus pneumoniae</i> pneumonia. The IgA, IgG and IgM values of each individual volunteer are connected with a line.</p

Levels of Pnc-specific plasmablasts and all plasmablasts in patients and controls.

<p>Percentage of pneumonia patients (n = 16) with indicated number of pathogen-specific ASC (A) and all ISC (immunoglobulin-secreting cells) (B) and percentage of healthy volunteers with indicated number of pathogen-specific ASC (C) and all ISC (D). ASC and ISC numbers are both presented as sum of IgA-, IgG- and IgM-secreting cells.</p

Geometric mean of pathogen-specific ASCs and all ISCs.

<p>The bars indicate geometric means (±SEM) of the number of ASCs and ISCs in the peripheral blood of patients with bacterial acute sinusitis, bacterial acute tonsillitis, and in healthy controls (IgA + IgG + IgM) ASCs or -ISCs/10⁶ PBMC). The patient samples were examined 7–14 days after the onset of symptoms. The number of volunteers from whom the data were pooled is shown under each bar. Differences between the distributions of the groups were tested with independent samples Median test (for ASC) or independent samples Kurskal-Wallis (for ISC). NS–p > .05.</p

Patient demographics, clinical picture and number of specific ASCs.

<p>Patient demographics, clinical picture and number of specific ASCs.</p

Comparison of proportions of α4β7-, L-selectin-, and CLA-expressing cells between ASCs and ISCs of the same patients.

<p>Data of patients with acute sinusitis and tonsillitis were pooled. The number of subjects is shown under each bar. Related-samples Wilcoxon Signed Rank test was used in comparisons between the same patients’ ASCs and ISCs; p-values are shown above the bars (NS = p > .05).</p