BIRMA-K3, a new monoclonal antibody for CD34 immunophenotyping and stem and progenitor cell assay

Application of cryo-compatible antibodies to human placenta paraffin sections

The hepes-glutamic acid buffer-mediated organic solvent protection effect (HOPE) -fixation and paraffin embedding technique has been described to expand possibilities for immuno-labellings due to low denaturation of proteins. In this study, the issue was addressed as to whether the HOPE technique could be a useful tool in placenta tissue-based studies when only cryo-compatible antibodies are available. Such antibodies can be used on cryostat sections only, giving results of considerably inferior morphological detail as compared to routinely fixed paraffin embedded tissue sections. Commercially available, only cryo-compatible, monoclonal antibodies against a conformational epitope of HLA-G (clone MEM-G/9) and leukocyte differentiation antigens CD56, CD163 and CD34 III were selected and applied to frozen sections, routinely formalin-fixed and HOPE-fixed paraffin sections. All tested antibodies immunolocalized their antigen on cryo sections and on HOPE-fixed but not formalin-fixed paraffin sections. The HOPE technique provides an excellent preservation of protein antigenicity together with well presented morphological details in paraffin embedded placenta tissues. The detection of native or conformation-dependent epitopes in paraffin sections expands the immunolocalization possibilities in placenta research and reproductive immunology.

Comparative evaluation of commonly used clones and fluorochrome conjugates of monoclonal antibodies for CD34 antigen detection

CD34+ cell enumeration is currently the most appropriate technique for hematopoietic graft quality control. At the same time, numerous CD34 mAb have become commercially available. This study was designed to compare the commonly used clones 8G12 and QBEND-10 with the new clones 581 and BIRMA-K3. All available fluorochrome conjugates were tested: FITC, PE, and PE-Cy5 or PerCP for QBEND, BIRMA, 581, and 8G12 and FITC and PE for 581. Bone marrow from healthy donors (n = 5) and leukapheresis samples (n = 16) were stained, according to each manufacturer's protocol and analyzed using the FACScan. The following parameters were evaluated: % CD34+ cells detected and percentage of deviation from the median within each sample; mean channel fluorescence intensity of the CD34+ cells; resolution index (median channel fluorescence intensity of CD34+ cells/monocytes), % overlapping of CD34+ cell and monocyte fluorescence; proportion of CD34+ events after blocking with the same unlabeled clone; values of compensation requirements. Tables with results for each evaluated parameter separately were created, and rank points were applied. These scores represented the quality performance of the studied clones and fluorochrome conjugates and may be summarized as follows: 581 and 8G12 produced the best results, followed by BIRMA-K3 and QBEND10. The fluorochrome sequence was PE, PE-Cy5, PerCP, and FITC. However, all PE conjugates of the studied clones provided highly comparable results and conditions for CD34+ cell enumeration. When antigen coexpression must be studied and another dye than PE must be applied for CD34+ cell discrimination, the PE-Cy5 conjugates should be preferred.