A new alternative for simultaneous immunohistochemical screening of 96 hybridoma clones for tissue-specific antibody productions selects a monoclonal antibody to insect corpus cardiacum

Digestion-Free Analysis of Peptides from 30-year-old Formalin-Fixed, Paraffin-Embedded Tissue by Mass Spectrometry Imaging

Formalin-fixed neuroendocrine tissues from American cockroaches ( Periplaneta americana) embedded in paraffin more than 30 years ago were recently analyzed by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), to reveal the histological localization of more than 20 peptide ions. These represented protonated, and other cationic species of, at least, 14 known neuropeptides. The characterization of peptides in such historical samples was made possible by a novel sample preparation protocol rendering the endogenous peptides readily amenable to MSI analysis. The protocol comprises brief deparaffinization steps involving xylene and ethanol, and is further devoid of conventional aqueous washing, buffer incubations, or antigen retrieval steps. Endogenous secretory peptides that are typically highly soluble are therefore retained in-tissue with this protocol. The method is fully "top-down", that is, without laborious in situ enzymatic digestion that typically disturbs the detection of low-abundance endogenous peptides by MSI. Peptide identifications were supported by accurate mass, on-tissue tandem MS analyses, and by earlier MALDI-MSI results reported for freshly prepared P. americana samples. In contrast to earlier literature accounts stating that MALDI-MSI detection of endogenous peptides is possible only in fresh or freshly frozen tissues, or exceptionally, in formalin-fixed, paraffin-embedded (FFPE) material of less than 1 year old, we demonstrate that MALDI-MSI works for endogenous peptides in FFPE tissue of up to 30 years old. Our findings put forward a useful method for digestion-free, high-throughput analysis of endogenous peptides from FFPE samples and offer the potential for reinvestigating archived and historically interesting FFPE material, such as those stored in hospital biobanks.

Development of a novel screening device permitting immunocytochemical screening of numerous culture supernatants during hybridoma production

A novel screening device is described which permits the simultaneous immunocytochemical processing of several hundreds or even thousands of hybridoma culture supernatants. The core of the screening apparatus is a foam-coated polymer plate that carries a 96-well pattern representing a modification of the actual 96-well template. This modification permits the use of conventional 26 X 76 mm microscopy glass slides. Each of these slides carries 24 carefully arranged histological sections. One 96-well plate is thus screened by mounting four of these slides in the apparatus during the primary antibody (i.e., culture supernatant) incubation stage. At all other stages of the immunocytochemical protocol, the slides are processed in the classical way. The screening apparatus has been used during the production of monoclonal antibodies against chicken pituitary glycoprotein hormones and against bovine neurohypophyseal peptides. In both instances, it proved to be the major contributory factor in the successful production of antibodies.