Vanadium pentoxide inhalation provokes germinal center hyperplasia and suppressed humoral immune responses

Vanadium, an important air pollutant derived from fuel product combustion, aggravates respiratory diseases and impairs cardiovascular function. In contrast, its effects on immune response are conflicting. The aim of our work was to determine if spleens of vanadium-exposed CD1 mice showed histological lesions that might result in immune response malfunction. One hundred and twelve CD-1 male mice were placed in an acrylic box and inhaled 0.02 M vanadium pentoxide (V2O5); actual concentration in chamber approximately 1.4 mg V2O5/m(3)) for 1 hr/d, twice a week, for 12 wk. Control mice inhaled only vehicle. Eight mice were sacrificed prior to the exposures. Eight control and eight V2O5-exposed mice were sacrificed 24 hr after the second exposure of each week until the 12-wk study was over. Another 8 mice that completed the 12-wk regimen were immunized with recombinant Hepatitis B surface antigen (HBsAg; three times over an 8-wk period) before sacrifice and analyses of their levels of anti-HBsAg antibody (HBSAb) using ELISA. In all studies, at sacrifice, blood samples were obtained by direct heart puncture and the spleen was removed, weighed and processed for H-E staining and quantitation of CD19 cells. The results indicated that the spleen weight of V2O5-exposed animals peaked at 9 wk (546 +/- 45 vs. 274 +/- 27 mg, p < 0.0001) and thereafter progressively decreased (321 +/- 39 mg at 12 wk, p < 0.001; control spleen = 298 +/- 35 mg). Spleens of V2O5-exposed animals showed an increased number of very large and non-clearly delimited germinal centers (that contained more lymphocytes and megakaryocytes) compared to those of control mice. In addition, their red pulp was poorly delimited and had an increase in CD19+ cells within hyperplasic germinal nodes. The mean HBsAb levels in immunized control mice were greater than that in the exposed hosts (i.e., OD = 0.39 +/- 0.03 vs. 0.11 +/- 0.05, p < 0.01). HBsAb avidity dropped to a value of 40 in V2O5-exposed animals vs. 86 in controls (p < 0.0001). We conclude that the chronic inhalation of V2O5, a frequent particle (PM(2.5)) component, induces histological changes and functional damage to the spleen, each of which appear to result in severe effects on the humoral immune response.