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Presence of eosinophilic precursors in the human thymus: Evidence for intra‐thymic differentiation of cells in eosinophilic lineage
Author(s) -
Lee Inchul,
Yu Eunsil,
Good Robert A.,
Ikehara Susumu
Publication year - 1995
Publication title -
pathology international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.73
H-Index - 74
eISSN - 1440-1827
pISSN - 1320-5463
DOI - 10.1111/j.1440-1827.1995.tb03518.x
Subject(s) - pathology , eosinophilic , myeloid , cd34 , peripheral blood mononuclear cell , cd33 , promyelocyte , flow cytometry , biology , population , stem cell , immunology , microbiology and biotechnology , medicine , in vitro , biochemistry , environmental health
The distribution of myeloid cells in the human thymus was investigated by light and electron microscopy, immuno‐histochemistry, andlor flow cytometry. A series of 74 thymic samples, from newborn to 37 year old patients, were studied. By light microscopy, aggregates of mononuclear cells were frequently present in intralobular septa and outer medulla. Among those cells, eosinophilic precursors (promyelocyte, myelocytes and metamyelocytes) were readily identified. These immature granular cells were present in all pre‐invo‐lutional thymi, and were particularly frequent in the thymi of patients who were younger than 5 years of age. The cells made up 30–50% of the total eosinophilic population and were frequently observed asagroupof cells at variousstages of differentiation, suggesting that they differentiate from preexisting precursors in the thymus. These eosinophilic precursors were mostly located in the intralobular septa and f ibroreticular network at the corticomedullary junction, while mature eosinophils were scattered throughout the thymus. Flow cytometric analyses, using stem cellenriched preparations, showed that cells expressing CD33 or CD34 constituted on average 2.55% and 3.33% (0.09% and 0.12% of the total cells), respectively. CD33+/CD34+ coexpressors were also identified, and they constituted 0.36% of the analyzed cells (0.01% of the total cells). No statistical difference in the proportions of CD33+ andlor 34′ cells was noted between any age groups. It is concluded that eosinophilic precursors present in the thymus differentiate into cells in the eosinophilic lineage in particular areas such as the intralobular septa and f ibroreticular network of the outer medulla in pt'ein‐volutional human thymi.