The use of quantum dots for immunochemistry applications

Immunocytochemistry and histochemistry are two most valuable immunochemistry techniques routinely used in biological laboratories. These techniques rely on the use of antibodies to label epitopes of interest in cells. At present, there is a wide range of commercially available organic dyes for labeling antibodies. However, limited extinction coefficients of organic dyes often make it difficult to achieve the optimal exposure and therefore fluorescence detection limit. Quantum dots (QDs) are fluorescent semiconductor nanocrystals which are advantageous over the organic fluorescent dyes in many aspects, principally their long-term luminescence stability, high brightness, and multicolor detection. Here, we describe the use of QDs for immunocytochemistry applications. We used three different antibodies-anti-β-tubulin monoclonal antibody for visualizing the microtubule network, the GM130 antibody for staining the Golgi complex, and the EEA1 antibody for detecting the endosomal system. We use the anti-mouse IgG antibody directly conjugated to QD655 quantum dots or anti-mouse IgG conjugated to biotin for tertiary detection with streptavidin-conjugated QD655.

Immunohistochemical evaluation of macrophage activity and its relationship with apoptotic cell death in the polar forms of leprosy

The objective of the present study was to investigate the correlation between macrophage activity and apoptosis in the polar forms of leprosy because the immunopathological phenomena involved in these forms are still poorly understood. For this purpose, 29 skin biopsy samples obtained from patients with the polar forms of leprosy were analyzed. Macrophage activity and apoptosis were evaluated by immunohistochemistry using lysozyme, CD68, iNOS and caspase 3 as markers. The nonparametric Mann-Whitney test and Spearman's linear correlation test were used for statistical analysis. The results suggest that the apoptosis rate is under the direct influence of macrophage activity in lesions of patients with the tuberculoid form. In contrast, in lepromatous lesions other factors seem to induce programmed cell death, possibly TGF-beta. Further studies are necessary to identify additional factors involved in the immunopathogenesis of leprosy.

State of the art in antigen retrieval for immunohistochemistry

The masking effects of antigens by chemical fixation, processing, embedding media interactions, represent a serious problem for immunohistochemical purposes. Fortunately, different approaches in antigen retrieval exist. These techniques are relatively recent and continuously expanding. This review focuses on the present state of the art in antigen retrieval methods for immunohistochemistry in light and electron microscopy. Moreover, a brief discussion on the chemical aspects of fixation, mechanism of retrieval, as well as its efficacy, is given.

Immunoperoxidase versus immunofluorescence in the assessment of human renal biopsies

BACKGROUND

For half a century, immunofluorescence (IF) on frozen sections has been the gold standard for immunohistochemical evaluation of renal biopsy specimens. In routine diagnostic immunohistopathologic evaluation, traditional IF has been replaced to a large extent by immunoperoxidase (IP) methods applied to paraffin sections of formaldehyde-fixed tissue. This is caused in part by the practical disadvantages inherent in the IF method, eg, separate tissue specimen and handling, UV microscopy, fading and impermanence of the label-making archiving, and difficult later investigation. Our aim for the present study is to evaluate IP as an alternative to IF in the diagnostic assessment of renal biopsy specimens.

METHODS

Proteolytic antigen retrieval, antibodies effective on deparaffinized sections, a sensitive detection system (Dako EnVision HRP; Dako, Copenhagen, Denmark), and a standardized and rigorously controlled procedure were applied to a series of renal biopsy specimens (n = 81) previously classified by means of light microscopy (LM) and IF. Staining for immunoglobulin G (IgG), IgA, IgM, C1q, and C3c were recorded as positive or negative for IF and IP in paired proportions, presuming that IF was the test standard.

RESULTS

Concordant observations were 71% for all (282 of 398 observations), 82% for IgG (65 of 79 observations), and 89% for IgA (72 of 81 observations). The majority of discordant observations (74 of 116 observations) were positive by means of IP, with mesangial deposits of IgM and C1q that were not found by IF. Statistically, there was no significant difference in outcomes between IF and IP for IgG, IgA, and C3c ( P > 0.2). In addition, IP staining allowed simultaneous evaluation of tissue by LM and therefore correlation between tissue structure and immune deposits not readily attained by IF.

CONCLUSION

In the present study, it is documented that for the detection of IgG, IgA, and C3c, IP applied to protease-digested deparaffinized sections of formaldehyde-fixed renal tissue is, with few exceptions, equal to IF on frozen sections. The EnVision HRP method used here is several times more effective in terms of primary antibody dilution than earlier existing IP methods, and because the avidin-biotin system is not involved, very little nonspecific background staining will occur. Discordant observations (116 of 398 observations; 29%) were in the majority (91 of 116 observations) due to positive IP findings of IgM and C1q, which deserve additional investigation.