SUMMARY Background: The primary
and secondary immunoglobulin repertoires represent an
important basis of the pathogen defence in the vertebrate.
The mucosa-associated lymphoid tissue plays a crucial role in
the establishment and maintenance of mucosal homeostasis
against invasive infections. Inside mucosal tissues,
Immunoglobulin A (Ig A) is the predominating immunoglobulin
that is secreted into the blood plasma, as well as onto the
mucous membrane. The differentiation of antigen-activated
B-cells into plasma and memory cells allows a quicker and
more effective immune response in case of a recurrent
confrontation with the same pathogen. Basic mechanisms
concerning the development of B-cell and antibody repertoires
are still unclear. Objective: It remains uncertain which
selective pressure acts upon the B-cell repertoire during the
class switch recombination from IgM to IgA in germinal
centres. Furthermore it is unknown which criteria drive the
recruitment of lymphocytes into the pool of IgA producing
memory and plasma cells. In this work, we tested the
hypothesis that subpopulations of IgA producing memory and
plasma cells are not recruited by chance, but on the basis of
their antigen binding properties. Methods: IgM producing
B-cells as well as IgA producing memory and plasma cells were
separated from Peyer’s patches of four adult BALB/C wildtype
mice using flow cytometry. Using reverse transcriptase-PCR,
we selectively amplified and cloned IgM and IgA transcripts
of the immunoglobulin heavy chains. The transcripts were
sequenced and nucleotide sequences were compared with the
IMGT databases of germline sequences (Alignment via IMGT
VQuest). Results: We collected a total number of 413
immunoglobulin sequences in four independent experiments of
which 323 (78%) were unique. The IgA sequences of memory and
plasma cells showed a significantly lower clonal diversity
than IgM sequences (74% and 72% vs. 94%; p <0.01). IgA
sequences of memory and plasma cells contained more somatic
mutations than IgM sequences (37‰ and 35‰ vs. 14‰, p
<0.01). IgA transcripts from memory cells contained a
lower number of random, so-called n-nucleotides within the
CDR3-regions than IgA transcripts from plasma cells (p
<0.01). In comparison t...