BackgroundFlow cytometric analyses with monoclonal antibodies were so far mainly restricted to cell surface molecules. Intracellular structures such as cytoplasmic or nuclear enzymes, oncoproteins, cytokines, immunoglobulins etc. were largely excluded from such studies. Also excluded from flow cytometric studies were cytoplasmic localizations of well-established membrane molecules like CD3 and CD22, which, in their cytoplasmic form, are the most reliable lineage markers in undifferentiated leukemia. With the FIX&PERM® Kit flow cytometric analysis of intracellular antigens has become as easy as surface antigen studies. The only prerequisite is the availability of suitable antibody conjugates. Most of the available monoclonal antibody conjugates can be used with the FIX&PERM® Kit, some determinants are sensitive, however, to the fixation step involved. This and the optimal fixation time have to be tested for each reagent.

ProductThis FIX&PERM® Cell Fixation and Permeabilization Kit contains 2 reagents: Fixation Medium (Reagent A) and Permeabilization Medium (Reagent B). It is intended for first fixing cells in suspension with Reagent A and then permeabilizing the cell membranes with Reagent B. This procedure gives antibodies access to intracellular structures and leaves the morphological scatter characteristics of cells intact. Specific formulations reduce background staining and allow simultaneous addition of permeabilization medium and fluorochrome labeled antibodies. FIX&PERM® is suitable for the analysis of normal and malignant leukocyte populations derived from various human biological samples (blood, bone marrow and others) using flow cytometry. Results must be put within the context of other diagnostic tests as well as the clinical history of the patient by a certified professional before final interpretation.Format: 4 x 5ml vial of Fixation Medium (Reagent A) and 4 x 5ml vial Permeabilization Medium (Reagent B). FIX&PERM® Reagents are designed for use with all commercially available flow cytometers. Alignment and compensation should be performed according to manufacturer´s instructions.The quality of each FIX&PERM® Lot is determined by fixation and permeabilization of well defined blood samples from representative donors and subsequent comparison of forward and side scatter characteristics of obtained leukocytes, as well as immunostaining efficiency for several membranous and cytoplasmic antigensFormulation: 4 x 5ml vial of Fixation Medium (Reagent A) and 4 x 5ml vial Permeabilization Medium (Reagent B). FIX&PERM Reagents are designed for use with all commercially available flow cytometers. Alignment and compensation should be performed according to manufacturer

ApplicationBiological fluids (blood, bone marrow, and others) must be collected under sterile conditions. Anticoagulation with EDTA or heparin is recommended. The samples should be stored at room temperature until used. For optimal results, samples should be processed and analyzed within 24 hours. Samples with high numbers of non-viable cells might cause false results, such cases require determination of cell viability with e.g. propidium iodide. All biological samples have to be handled with caution. Always consider them as potentially infective. Use appropriate precautions such as gloves, lab-coat, etc.

Fixation, permeabilization and staining procedure:

• For each sample to be analyzed add 50 µl of whole blood, bone marrow or mononuclear cell suspension in a 5ml tube
• Add 100 µl of Reagent A (Fixation Medium, stored and used at room temperature)
• Incubate for 15 minutes at room temperature
• Add 5ml phosphate buffered saline and centrifuge cells for 5 minutes at 300 g
• Remove supernatant and add to cell pellet 100 µl Reagent B (Permeabilization Medium) and 20 µl of the appropriate Nordic-MUbio monoclonal antibody conjugate
• Vortex at low speed for 1-2 seconds
• Incubate for 15 minutes at room temperature
• Wash cells with phosphate buffered saline as described above
• Remove supernatant and resuspend cells in sheath fluid for immediate analysis or resuspend cells in 0.5 ml 1.0 % formaldehyde and store them at 2-8°C in the dark. Analyze fixed cells within 24 hours.

Comments: Special cases (diluted bone marrow samples, other samples containing low soluble protein) might benefit from replenishment with plasma components before the FIX&PERM® treatment in order to create a milieu, which more closely resembles the stuation in anti-coagulated blood. For that pupose addition of IgG preparations (e.g. Beriglobulin P, ZLB Behring, final concentration 10mg/ml) and human serum albumin (e.g. human albumin "Behring" 20% – infusion solution, final concentration 40mg/ml) is recommended.

ReferencesRecent application paper:Nies KPH, Kraaijvanger R, Lindelauf KHK, Drent RJMR, Rutten RMJ, Ramaekers FCS, Leers MPG. Determination of the proliferative fractions in differentiating hematopoietic cell lineages of normal bone marrow. Cytometry A. 2018 Sep 3. doi: 10.1002/cyto.a.23564.

Here you can find more references and information about FIX&PERM.