relazione ufficiale - S.I.O.e.Ch.CF.

D. Passàli et al.
The knowledge of the role played by the polymeric immunoglobulin receptor
(pIgR) is enlightening and helps understand some of the strategies implemented
by the Streptococcus, which has devised an ingenious internalization strategy by
taking advantage precisely of the pIgR recycling process 3,4 :
1. through the PspC adhesin (also named SpsA), Streptococcus pneumoniae
binds the human pIgR immediately after releasing the sIgA;
2. the pIgR-pneumococcus complex undergoes endocytosis by the nasopharyngeal
epithelial cell;
3. the pIgR-pneumococcus is retrograded from the apical side to the basal
side of the cell (Fig. 2);
4. the pneumococcus remains buried inside the epithelial cell.
Nontypeable Haemophilus influenzae (NTHI), which is also responsible for
acute otitis media, sinusitis and bronchitis, is a non encapsulated gram-negative
cocco-bacillus that was able to select different modes of internalizing into
the respiratory epithelium. One of the most interesting strategies involve the
ICAM-1 (intercellular adhesion molecule-1) 5 , which mediates reversible adhesion
and trasduction between inflammatory and immune cells in order to recruit
leukocytes and to promote T cell development. The NTHI binds to the ICAM-1
through a fimbria, drastically reducing the number of receptor sites available to
the leukocytes 5 .
To enter host cells, Mycoplasma pneumoniae has chosen as mediator the surfactant
protein-A, which is capable of reducing surface tension at the alveolar
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Fig.2: pIgR-pneumococcus is retrograded from the apical side to the basal side of the cell.