A12 A novel microarray containing 82 cluster of differentiation (CD) antibodies has been used to obtain extensive immunophenotypes of leukemia cells. Leukocytes are captured on antibody dots corresponding to particular cell surface molecules to give a dot pattern that is the immunophenotype. Samples from the peripheral blood and bone marrow of 733 leukemia patients were analyzed. Discriminant Function Analysis of the expression profiles from these 733 patients and 63 normal subjects were clustered and showed high levels of consistency with diagnoses obtained using conventional criteria. The overall levels of consensus for classification using the microarray compared with established criteria were 93.9% (495/527 patients) for peripheral blood and 97.6% (201/206 patients) for bone marrow aspirates, showing that the extensive phenotype alone was frequently able to classify the disease when the leukaemic clone was the dominant cell population. Immunophenotypes for neoplastic cells were distinguishable from normal cells when the leukaemic count was at least 5 X 10(9) cells/L in peripheral blood, or 20% of cells obtained from bone marrow aspirates. This technique will be a useful adjunct to flow cytometry and other methods when an extensive immunophenotype of leukemia cells is required. An extensive immunophenotype alone may be sufficient for diagnosis of most leukemias.

A cluster of differentiation (CD) antibody microarray called the DotScan microarray has been developed that enables an extensive immunophenotype to be obtained for a suspension of leukocytes in a single analysis. For a leukemia with a leukemia count of greater than 10 x 10(9)/L, the immunophenotype obtained is essentially that of the leukemic clone. The antibody microarray is printed as microscopic (10 nL) dots on a nitrocellulose film on a microscope slide. Cells are captured by the immobilized antibodies and a dot pattern is recorded with an optical array reader giving the immunophenotype of the leukemia. Procedures are being developed that should enable diagnosis of myeloid leukemias by comparison of the dot pattern obtained from an unknown blood sample with a library of consensus patterns for the common leukemias.

Cluster of differentiation (CD) antigens are expressed on cells of myeloid and lymphoid lineages. As most disease processes involve immune system activation or suppression, these antigens offer unique opportunities for monitoring host responses. Immunophenotyping using limited numbers of CD antigens enables differentiation states of immune system cells to be determined. Extended phenotyping involving parallel measurement of multiple CD antigens may help identify expression pattern signatures associated with specific disease states. To explore this possibility we have made a CD monoclonal antibody array and scanner, enabling the parallel immunophenotyping of leukocyte cell suspensions in a single and rapid analysis. To demonstrate this approach, we used the specific example of patients infected with human immunodeficiency virus type-1 (HIV-1). An invariant HIV-induced CD antigen signature has been defined that is both robust and independent of clinical outcome, composed of a unique profile of CD antigen expression levels that are both increased and decreased relative to internal controls. The results indicate that HIV-induced changes in CD antigen expression are disease specific and independent of outcome. Their invariant nature indicates an irreversible component to retroviral infection and suggests the utility of CD antigen expression patterns in other disease settings.