Sensitivity and specificity of immunohistological methods on freeze-dried paraffin sections

Cryofixed, freeze-dried and paraffin-embedded skin enables successful immunohistochemical staining of skin basement membrane antigens

Conventional chemical fixation and paraffin-embedding procedures give good preservation of morphology, although the antigenicity of many proteins in the tissue sample is destroyed. On the other hand, fresh frozen sections can preserve the antigenicity, but provide poor morphological preservation. To overcome this dilemma, cryofixation and freeze drying were used on human skin tissue, applying methodology which has only been used to study lymphoid tissue. First, fresh human skin was cryofixed in liquid isopentane (-160 degrees C) cooled by liquid nitrogen. The skin was then freeze-dried at -40 degrees C and 10(-2) atmospheric pressure for 72 h, followed by embedding in paraffin. Sections 4 microns thick taken from this cryofixed, freeze-dried, and paraffin-embedded skin were stained with hematoxylin-eosin or used for immunolabeling with antibodies against basement membrane antigen, including type IV and type VII collagen, bullous pemphigoid antigen, epidermolysis bullosa acquisita antigen, and GB3 antigen. The morphological preservation of these sections was as good as that of routine formalin-fixed and paraffin-embedded skin sections. The basement membrane was clearly immunostained with all antibodies used, and the intensity of the reaction was as strong as that seen in frozen sections. Evaluation of antigen distribution in conjunction with the detailed skin structure was therefore possible in the same sections.

Analysis of leukocyte surface antigens on ethanol-fixed paraffin-embedded tissue material

Ethanol-fixed paraffin-embedded specimens of human tissues were studied whether the surface antigens of leukocytes in these tissues can be stained and analyzed. Three-layer indirect immunoperoxidase staining was performed on the ethanol-fixed paraffin-embedded sections by the use of several monoclonal antibodies for whole human leukocytes (Dako LC), B cells (Dako CD-22, 4KB5, and L26; Leu 14), T cells and their subsets (Dako UCHL-1, T1, T3, T4 and T8; Leu 4, 3a and 2a) and monocyte/macrophage lineage (Dako macrophage, Leu M1, M3 and M5). The results were compared with those on fresh-frozen sections. No essential differences were obtained between the paraffin-embedded and the fresh frozen sections stained by the following antibodies; Dako LC for whole human leukocytes; Dako UCHL-1, T3 and Leu 4 for T cells; Dako CD22, 4KB5, L26 and Leu 14 for B cells; Dako macrophage, Leu M1 and M5 for monocyte/macrophage lineage. On the other hand, the subsets of T cells could only be detected on the fresh-frozen sections. The results of the leukocyte analysis on the paraffin-embedded specimens of several renal diseases were very similar to those reported by other investigators on fresh-frozen sections or PLP-fixed materials. Thus, by the use of appropriate monoclonal antibodies, the ethanol-fixed paraffin-embedded material can be used for leukocyte analysis except for the definition of T cell subsets.

A freeze-dried paraffin-embedded tissue technique for immunohistochemical studies requiring unfixed tissue from the nervous system

Immunohistochemical studies using monoclonal antibodies against epitopes in neural tissues frequently require tissue which has not been fixed in formalin. In the past, such studies have been performed on frozen (cryostat) sections despite the general loss of morphological preservation compared with paraffin sections. In the present report, a detailed, versatile method for obtaining improved morphological preservation of "unfixed" neural tissue is described which utilizes freeze-dried paraffin-embedded sections (a modified Altmann-Gersh technique). The advantages of using mercury flotation of freeze-dried sections are particularly stressed.

Intensification of 3,3'-diaminobenzidine precipitation using the ferric ferricyanide reaction, and its application in the double-immunoperoxidase technique

As in double-immunoperoxidase methods, colour mixing usually indicates unwanted interactions between reagents of the first and second sequences, it is desirable to prevent such superimposition of colours by eliciting adequate colour intensity in the first immunoperoxidase sequence. The brown oxidation product of 3,3'-diaminobenzidine (DAB) in the first immunoperoxidase sequence can be intensified by applying the ferric ferricyanide reaction, resulting in intense greenish-blue staining. When the primary antibody is used at a sufficient concentration, cells labelled in the first sequence do not cross-react with the red chromogen, 3-amino-9-ethylcarbazole (AEC), used in the second sequence. Thus, this double-immunoperoxidase method results in different cell populations being clearly labelled in contrasting colours. Primary antibodies from the same species and the same type of link antibodies can be used in the two separate immunoperoxidase sequences. When primary antibodies raised in different species and two types of link antibodies are used, the method can, without loss of sensitivity, be shortened by performing the first two incubation steps simultaneously.

Simultaneous visualization of vascular permeability change and leukocyte egress in the central nervous system during autoimmune encephalomyelitis

An unresolved issue in the study of demyelinating disease is whether blood-brain barrier damage is dependent upon the migration of inflammatory cells into the central nervous system (CNS). In a study of experimental autoimmune encephalomyelitis (EAE) in rabbits, a freeze-dried, paraffin-embedded tissue technique was exploited to enable (1) the immobilization of intravenously injected sodium fluorescein tracer, as an index of vascular permeability; and (2) an effective labeling by monoclonal antibodies of both T-lymphocytes and mononuclear phagocytes in "unfixed" neural tissue. Using these newly combined methods, evidence was found that increased vascular permeability in the CNS during EAE occurs concomitantly with, and not prior to, infiltration by mononuclear phagocytes.

Studies on endometrial cells in human pregnancy by monoclonal antibodies

By immunizing mice with endometrial cells from pregnant women, we obtained two hybridoma clones, 9D3 (IgG1) and 9E3 (IgG3), secreting monoclonal antibodies (MoAbs) that selectively stained endometrial stromal cells having prolactin in their cytoplasm, but did not stain glandular epithelium nor small lymphoid cells. From examination of tissues, cells and cell lines, it was found that 9E3 antigen was broadly distributed among various mesenchymal cells, while 9D3 antigen was distributed on a more restricted spectrum of mesenchymal cells, skin basal cells and a promonocytic cell line (U937). Neither of these antibodies stained peripheral blood cells, bone marrow cells or endometrium of the proliferating phase. Furthermore, 9D3 MoAb reacted with all melanoma cell lines and squamous cell lines examined. The antigenic molecule that was recognized by 9D3 MoAb had a molecular weight of 94,000.

Demonstration of light chain monotypia in B cell non-Hodgkin's lymphomas using unfixed freeze-dried and formalin-fixed trypsinised paraffin sections

Immunohistological light chain analysis was carried out in 55 patients with non-Hodgkin's lymphoma of B cell origin. Unfixed freeze-dried paraffin sections were used to detect surface Ig and formaldehyde-fixed trypsinised sections to detect cytoplasmic Ig. Cytoplasmic Ig was seen inconstantly in freeze-dried paraffin sections. There was complete agreement with regard to the type of light chain between freeze-dried and formaldehyde-fixed trypsinised sections. Immunohistology showed the monotypic immunoglobulin light chains in 83% of cases when unfixed freeze-dried paraffin sections were used for sIg demonstration while only in 45% of cases when formaldehyde-fixed material was used for cIg detection. The efficiency of sIg demonstration in unfixed freeze-dried paraffin sections was comparable with that based on unfixed cryostat sections or on cell suspensions when the lymphocytic lymphoma/CLL group was excluded from the evaluation. The relatively low frequency of monotypic sIg positivity obtained in this group (12/19) is due to the low density of surface Ig in CLL lymphocytes.