Arylsulfatase B Is Present in Crystalloid-Containing Granules of Human Eosinophil Granulocytes

Abstract

Eosinophil granulocytes are characterized by large crystalloid-containing granules whose major contents of highly cationic proteins may play a role in allergic reactions and parasitic infections. Human eosinophils are also rich in arylsulfatase B whose enzymatic activity is localized to a population of small type cytoplasmic granules and used as a marker for such organelles. We utilized immunoelectron microscopy to investigate its subcellular distribution in human eosinophils. The arylsulfatase B antigen was found to be concentrated to both the crystalloid core and the matrix of crystalloid-containing granules as well as in small type granules. Therefore arylsulfatase seems to be present primarily in crystalloid-containing granules in a possibly inactive form (but detected by antibodies) that is converted to an enzymatically active form, e.g. during secretion and formation of small type granules which may derive from the former granules.

Contemporary understanding of the secretory granules in human eosinophils

“…Because specific granules did not exhibit cytochemical activity for arylsulfatase B, this enzyme was considered a marker for “small granules” in human eosinophils . Later, by using immunoelectron EM, it was demonstrated that arylsulfatase B was in fact primarily present within specific granules likely in an inactive form (detected by antibodies) in addition to “small granules” . These authors correctly predicted that “small type granules” might derive from specific granules during secretion when then the inactive form of arylsulfatase would be converted to an enzymatically active form .…”

Overview on the pathomechanisms of allergic rhinitis

“…Within the tissue, cytokines like IL-5 and GM-SCF keep eosinophils alive for several days or even weeks which overcome programmed cell death (apoptosis) [36, 37]. Mature eosinophils contain MBP [38], ECP [39], eosinophil-derived neurotoxin (EDN) [40], eosinophil peroxidase all of which play important roles in the immune mechanisms of allergic inflammation, especially in altering the surface epithelium. In addition, eosinophils synthesize and release cytokines such as IL-3, IL-5, GM-CSF [41], proinflammatory cytokines, chemokines (RANTES, IL-8, MIP-1α) [42] that play crucial roles in the late phase and on-going allergic inflammation.…”

Localization of Granule Proteins in Human Eosinophil Bone Marrow Progenitors

“…Histochemically detectable arylsulfatase activity is present in coreless granules as well, but not in core-containing (specific) granules o f eosinophils [8], However, by using specific antibodies, arylsulfatase B has been shown to be present in specific granules as well, presumably in a latent, enzymatically inactive form [15]. This finding suggests that small-type granules containing active arylsulfatase may be related to specific granules, con taining enzymatically inactive arylsulfatase [15]. The pre sent finding of arylsulfatase B in both coreless and corecontaining granules further supports the notion that corecontaining specific granules derive from primary granules in a maturational process.…”

“…Small-type granules contain unmasked, histochemically detectable arylsulfatase and acid phosphatase activity [14]. Histochemically detectable arylsulfatase activity is present in coreless granules as well, but not in core-containing (specific) granules o f eosinophils [8], However, by using specific antibodies, arylsulfatase B has been shown to be present in specific granules as well, presumably in a latent, enzymatically inactive form [15]. This finding suggests that small-type granules containing active arylsulfatase may be related to specific granules, con taining enzymatically inactive arylsulfatase [15].…”

“…Examples arc major basic protein (MBP), eosinophil peroxidase (EPO), and the eosinophil ribonucleases: eosi nophil cationic protein (ECP) and the eosinophil-derived neurotoxin (EDN). MBP has been demonstrated in the crys talloid core of specific eosinophil granules, while EPO, ECP, and EDN have been localized to the matrix of these granules [11,12], Arylsulfatase B, a lysosomal enzyme of eosinophils [6,13], is present both in specific core-contain ing granules and in a population of small-type eosinophil granules [14,15],…”