>Cytometrists, >I have two interesting cases that I would like some help with. >1. The first patient appears to be a new acute leukemia with very >large irregular cells. The bone marrow phenotypes CD13+,CD15+,CD33+,HLA DR+, >CD45+(bright),CD14 My4+ but CD14 Mo2 negative. >I would like to know others' experience with My4. Does it mark a >more immature monocytoid cell? Would you call this myelomono- >leukemia? >2. The second case is a patient with normal numbers of all cell >types in the peripheral blood but with two clearly different >populations of CD5+ cells--one very bright and the other dimmer but >still positive. They do not dual stain with B cell markers. In >1993 the patient showed a T cell beta gene rearrangement. If we had >not been aware of this we may not have worried so much about the >staining. Has anyone noticed this pattern of CD5 reactivity? >Thank you very much for your help. > >Michaeleen M. Collins See the following reference on the discordance between MY4 and LeuM3 epitopes, in relation to LPS binding capacity. I include the abstract. Basically, there are some monocyte cell lines which can bind My4 but not LeuM3. Interestingly, this pattern (My4+ LeuM3- UCHM1-) is also seen in airway DC and possibly blood DC precursors as well (ref.2), which suggests another phenotype possibility for your patient (although these are not to my knowledge CD15+). 1. T. Pedron, R. Girard and R. Chaby Variation of LPS-binding capacity, epitope expression, and shedding of membrane-bound CD14 during differentiation of human monocytes Journal of Immunology 1995 155 (3): 1460-71 The myeloid differentiation Ag CD14 is considered to play a critical role in the binding of LPS to monocytes. To determine if differences in LPS-binding capacities of cells could reflect a variability of CD14 molecules, we analyzed the interactions of various reagents with these molecules in human blood monocytes and in promyelocytic (HL60) and monocytic (THP-1) cell lines. The expression of CD14 epitopes was analyzed with the fluorescent anti-CD14 mAbs My4 and LeuM3. Expression of LPS-binding sites (LPS+ molecules) was detected with LPS-FITC. THP-1 cells stimulated with calcitriol (VitD3), as well as the majority of blood monocytes (50-90%) were My4+/LPS+. However, untreated THP-1 cells, and a substantial population (10-50%) of human monocytes from healthy donors, were My4+/LPS-, thus suggesting the existence of CD14 isoforms with different LPS-binding capacities. In line with this assumption, monocytes stimulated with PMA selectively shed LeuM3+ molecules, but almost no My4+ and LPS+ constituents. Analysis of monocytes after treatment with phosphatidylinositol-specific phospholipase C indicated that among CD14 molecules with LPS-binding capacity, some are susceptible and others are resistant to the enzyme, each type being mainly expressed by a different monocyte subset. Studies of uninduced and chemically induced THP-1 cells showed that wheat-germ agglutinin blocked the binding of My4 to constitutive, but not to chemically inducible CD14. The overall results suggest the existence of at least three different forms of CD14, which may reflect different stages of cell maturation. 2. J. M. van Haarst, H. J. de Wit, H. A. Drexhage and H. C. Hoogsteden Distribution and immunophenotype of mononuclear phagocytes and dendritic cells in the human lung American Journal of Respiratory Cell & Molecular Biology 1994 10 (5): 487-92 ______________________________________________ Dr William Smith Institute for Child Health Research (Company Limited by Guarantee ACN 009 278 755) Subiaco, Western Australia, 6008 PO Box 855 West Perth WA 6872 Ph 61 8 9340 8792/8388, Fax 61 8 9388 3414 email williams@ichr.uwa.edu.au ______________________________________________
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