Quantitation of Antibody-Secreting Cells in the Blood after Vaccination with a Haemophilus influenzae Type b Conjugate Vaccine

1365-3083

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The human B-lymphocyte response to proiein-conjugated polysaccharide antigens has not previously been studied at the cellular level. In order to do so, we developed and evaluated haemolytic plaque-forming cell assays detecting Haemophilus influenzae type b (Hib) capsular polysaccharide-specific antibody-secreting cells (AbSC) of the isotypes IgM, IgG, and IgA. The appearance of AbSC in the blood after vaccimation of adults with diphtheria toxoid-conjugated Hib polysaccharide was investigated. AbSC were detected from post-vaccination day 5 to day 14.IgA was the predominant isotype among these cells. IgM AbSC peaked slightly earlier (median day 7) than IgG and IgA AbSC (both day 8). On post-vaccination day 8 ihe numbers of AbSC were: IgA. 1217/106 mononuclear cells (median); IgG, 211; and IgM, 30 (n= 11). Similar isotype distribution has earlier been found after vaccination with pure capsular polysaccharides from Hib and pneumococci. The predominance of IgA AbSC in response to both conjugate and pure polysaccharide vaccines is probably due to reactivation of the same clones of IgA-committed memory B cells originally primed at the mucosa by natural exposure to the polysaccharide or cross-reacting antigens.

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