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Immunolocalization of serum amyloid A and AA amyloid in lysosomes in murine monocytoid cells: Confocal and immunogold electron microscopic studies
Author(s) -
Chronopoulos S.,
Laird D. W.,
AliKhan Z.
Publication year - 1994
Publication title -
the journal of pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.964
H-Index - 184
eISSN - 1096-9896
pISSN - 0022-3417
DOI - 10.1002/path.1711730412
Subject(s) - immunogold labelling , pathology , amyloid (mycology) , confocal , chemistry , electron microscope , ultrastructure , confocal microscopy , biology , microbiology and biotechnology , medicine , physics , optics
Murine AA amyloid (AA) protein represents the amino‐terminal two‐third portion of SAA 2 , one of the isoforms of serum amyloid A. Whether plasma membrane‐bound or lysosomal enzymes in activated murine monocytoid cells degrade SAA 2 to generate amyloidogenic AA‐like peptides is not clearly understood, although AA has been localized in the lysosomes. Here we show, using confocal and immunogold microscopy (IEM), that both SAA and AA localize in lysosomes of activated monocytoid cells from amyloidotic mice. Rabbit anti‐mouse AA IgG (RAA) and two monoclonal antibodies against murine lysosome‐associated membrane proteins (LAMP‐1 and LAMP‐2) were used to immunolocalize SAA/AA and lysosomes, respectively. Confocal analysis co‐localized both anti‐RAA and anti‐LAMP‐1/LAMP‐2 reactivities in the perikaryal organelles which by IEM proved to be electron‐dense lysosomes. LAMP‐1/LAMP‐2‐specific gold particles were also localized on lysosomal and perikaryal AA. The results suggest sequestration of SAA into the lysosomes. Since monocytoid cells are not known to phagocytose native amyloid fibrils, our results implicate lysosomes in AA formation.