CD1a

CD1a

a type I transmembrane protein found on thymocytes, Langerhans cells, brain astrocytes, and dermal cells that is involved in nonclassical antigen presentation or is a receptor for an undefined ligand or hormone; expressed in patients with T-cell acute lymphoblastic leukemia, histiocytosis X, and thymomas.
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Langerhans cells marked with S100 protein (nuclear and cytoplasmic staining [A]), CD1a (membranous staining [B]), and langerin (CD207) (membranous, granular cytoplasmic, and Golgi staining [C]) (original magnification X400 [A through C]).
Staining for CD1a, lysozyme, myeloperoxidase, CD34, CD3, CD79a, CD30, HMB-45, desmin, and high-molecular weight cytokeratins is negative.
The characteristic immunophenotype of LCH includes expression of CD1a, S100 protein, and langerin (CD207) (Figure, C and D).
but are distinguished by expression of CD1a and the presence of Birbeck granules, ultrastructurally.
Markers for Thymoma (Subtypes A, AB, B1, B2, and B3) (a) Antibodies Thymoma CKAE1/3 + CK19, CK5/6, and CK7 + (in type B1, B2, and B3 thymoma) EMA and CD57 - /+ CD5, CK20, TTF1, and CD70 - Ki-67 labeling index Low (in subtype A and AB tumor cells) Admixed cortical immature + for TdT, CD1a, CD99, CD5, CD4, CD8 T cells Admixed medullary mature + for CD3 and CD5, but--for TdT, CD1a, T lymphocytes CD99 p63 + PAX8 + Abbreviations: CD, cluster of differentiation; CK, cytokeratin; EMA, epithelial membrane antigen; PAX8, paired box gene 8; Tdt, terminal deoxynucleotidyl transferase; TTF1, thyroid transcription factor 1; +, greater than 75% of cases are positive; -, less than 5% of cases are positive; -/+, less than 50% of cases are positive.
It is associated with a rich lymphoid infiltrate and is S100 positive and CD1a negative.
A CD1a immunostain was ordered and the lesional cells were positive (Figure 1, D).
However, malignant cells in these cases all are positive for significant expression of histiocytic/dendritic cell markers, including CD1a, CD23, CD68, CD163, and S100.
On immunohistochemistry, RDD was positive for both S-100 and CD68 proteins but negative for CD1a.
Tumour cells were negative for CD117, DOG1, CD1a, SMA and ALK.
blasts were also positive for CD5 and negative for surface CD3, CD1a, CD2, CD4, and CD8.
The following monoclonal antibodies were used: CD1a (DakoCytomation, Glostrup, Denmark), CD34, CD86, HLA-DR (BD Biosciences, San Jose, USA), all FITC-conjugated; CD14 (DakoCytomation), CD54, CD80 (BD Biosciences), all PE-conjugated.