Sources/Clones
Biogenex (HHF35), Dako (HHF35), Diagnostic Biosystems (HHF35), Enzo (HHF35), Biogenesis, Sanbio (SA1C1), and Zymed (ZMSA-5, ZCA34, ZSA-1).
Fixation/Preparation
The antibody HHF35 is immunoreactive in fixed paraffin-embedded tissue sections and staining is enhanced following HIER.
Background
There are at least six different actin isotypes in mammals. They are four isotypes found exclusively in muscular tissues and includea-skeletal, a-cardiac, and a and g-smooth muscle actins and two other isotypes, b-and g-cytoplasmic actin, found in most cell types, including non-muscle cells of the body. Early antiactin antibodies were polyclonal and did not distinguish among various actin isotypes and were of low sensitivity and specificity. Various monoclonal antibodies have now been described and the most widely used is clone HHF35, available commercially, which recognizes a common epitope ofa-skeletal, a-cardiac and a- and g-smooth muscle actin isotypes (Tsukada et al, 1987). This antibody labels myoepithelial and smooth muscle cells as well as leiomyomas and leiomyosarcomas. Muscle-specific actins (MSA) have also been described in pericytes, reactive myofibroblasts, and skeletal and cardiac muscle. Positive staining cells have been reported in the deep ovarian cortical stroma and theca externa of secondary ovarian follicles, alveolar soft part sarcoma, epithelioid sarcoma, infantile digital fibromatosis, ovarian sclerosing stromal tumors and Kaposi's sarcoma, representing either myofibroblasts or pericytes in these conditions. Glomus tumors stain positive for MSA, a finding which supports a smooth muscle derivation of these tumors (Dervan et al, 1989), and the variable extent of MSA staining observed in malignant mesothelioma (Kung et al, 1995) and malignant fibrous histiocytoma has been attributed to myofibroblastic differentiation in these tumors. Actin staining of unequivocal tumor cells has been reported in occasional cases of metastatic endometrial stromal sarcoma and malignant peripheral nerve sheath tumor but it has not been ascertained if these findings represent aberrant actin expression of tumor cells or crossreactivity of antiactin antibodies. MSA has also been observed in the cells of the capsule of the liver, kidney and spleen and in decidual cells, some stromal cells of chorionic villi and the so-called fibroblastic reticulum cells of lymph nodes and spleens.
Applications
The increased sensitivity and specificity of newer monoclonal antibodies allow the use of anti-MSA antibodies in the identification of pleomorphic spindle cell tumors. Because of varying sensitivities, it is best to employ MSA with other myogenic markers such as smooth muscle actin and desmin when examining tumors, which potentially confuse with rhabdomyosarcoma (RMS), leiomyosarcoma (LMS) and myofibroblastic tumors (Azumi et al, 1988). Much of the current controversy as to which of these markers is the most sensitive for myogenic differentiation stems from the fact that the expression of the individual markers varies with the site of origin of the tumor (Rangdaeng & Truong, 1991). For example, most soft tissue and uterine LMS contain predominantlya- smooth muscle actin but those from the gastrointestinal tract show onlyb and g non-muscle actins and would thus be negative for HHF35. Myofibroblasts show heterogeneous immunophenotype and may be positive for vimentin only; for vimentin and a- smooth muscle actin; for vimentin and desmin; or for vimentin, desmin anda- smooth muscle actin (Skalli et al, 1989). Myofibroblastic proliferations such as nodular fasciitis may display characteristic peripheral/subplasmalemmal staining for muscle actin, yielding a ''tram track" appearance (Leong & Gown, 1993). Increased expression of MSA has been correlated with mesangial cell injury and proliferation in both rats and humans and can be employed as a marker of mesangial cell injury, activation and proliferation (Alpers et al, 1992).
Comments
Zenker's fixative appears to cause a marked decrease in the intensity of MSA staining. HIER enhances immunostaining and simple heating in distilled water at 60 C overnight or in ZnSO4 at 90 C for 10 min produces the best results. False-positive reactivity with clones HHF35 and 1A4 has been reported in non-Hodgkin's lymphoma, a problem attributed to contaminating antibodies, partial antibody degradation or excess antibody concentration which may occur with ascitic fluid preparations of anti-MSA (Sheehan & O'Brian, 1995). The problem was not observed in tissue culture supernatant antibodies and was abolished by the addition of 50 mmol/l of EDTA to the prediluted antibody.
References
•Alpers CE, Hudkins KL, Gown AM, Johnson RJ 1992. Enhanced expression of "muscle-specific" actin in glomerulonephritis. Kidney International 41: 1134-1142.
•Azumi N, Ben-Erza J, Battifora H 1988. Immunophenotypic diagnosis of leiomyosarcomas and rhabdomyosarcomas with monoclonal antibodies to muscle specific actin and desmin in formalin-fixed tissue. Modern Pathology 1: 469-474.
•Dervan PA, Tobbia IN 1989, Casey M, et al. Glomus tumors: an immunohistochemical profile of 11 cases. Histopathology 14: 483-491.
•Kung IT, Thallas V 1995, Spencer EJ, Wilson SM. Expression of muscle actins in diffuse mesotheliomas. Human Pathology 26: 565-570.
•Leong AS-Y, Gown AM 1993. Immunohistochemistry of "solid" tumours: poorly differentiated round cell and spindle cell tumors I. In: Leong AS-Y (ed). Applied Immunohistochemistry for surgical pathologists. London: Edward Arnold, pp24 72.
•Rangdaeng S, Truong LD 1991. Comparative immunohistochemical staining for desmin and muscle specific actin. A study of 576 cases. American Journal of Clinical Pathology 96: 32-45.
•Sheehan M, O'Brian DS 1995. False-positive immunoreactivity with muscle-specific actins in non-Hodgkin's lymphoma. Archives of Pathology and Laboratory Medicine 119: 225-228.
•Skalli O, Schurch W, Seemeyer TA et al 1989. Myofibroblasts from diverse pathologic settings are heterogenous in their content of actin isoforms and intermediate filament protein. Laboratory Investigation 60: 275-285.
•Tsukada T, Tippens D, Gordon D et al 1987. HHF35, a muscle-specific actin-specific monoclonal antibody. I. Immunocytochemical and biochemical characterisation. American Journal of Pathology 126: 51-60.
Bibliografia
Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.
Biogenex (HHF35), Dako (HHF35), Diagnostic Biosystems (HHF35), Enzo (HHF35), Biogenesis, Sanbio (SA1C1), and Zymed (ZMSA-5, ZCA34, ZSA-1).
Fixation/Preparation
The antibody HHF35 is immunoreactive in fixed paraffin-embedded tissue sections and staining is enhanced following HIER.
Background
There are at least six different actin isotypes in mammals. They are four isotypes found exclusively in muscular tissues and includea-skeletal, a-cardiac, and a and g-smooth muscle actins and two other isotypes, b-and g-cytoplasmic actin, found in most cell types, including non-muscle cells of the body. Early antiactin antibodies were polyclonal and did not distinguish among various actin isotypes and were of low sensitivity and specificity. Various monoclonal antibodies have now been described and the most widely used is clone HHF35, available commercially, which recognizes a common epitope ofa-skeletal, a-cardiac and a- and g-smooth muscle actin isotypes (Tsukada et al, 1987). This antibody labels myoepithelial and smooth muscle cells as well as leiomyomas and leiomyosarcomas. Muscle-specific actins (MSA) have also been described in pericytes, reactive myofibroblasts, and skeletal and cardiac muscle. Positive staining cells have been reported in the deep ovarian cortical stroma and theca externa of secondary ovarian follicles, alveolar soft part sarcoma, epithelioid sarcoma, infantile digital fibromatosis, ovarian sclerosing stromal tumors and Kaposi's sarcoma, representing either myofibroblasts or pericytes in these conditions. Glomus tumors stain positive for MSA, a finding which supports a smooth muscle derivation of these tumors (Dervan et al, 1989), and the variable extent of MSA staining observed in malignant mesothelioma (Kung et al, 1995) and malignant fibrous histiocytoma has been attributed to myofibroblastic differentiation in these tumors. Actin staining of unequivocal tumor cells has been reported in occasional cases of metastatic endometrial stromal sarcoma and malignant peripheral nerve sheath tumor but it has not been ascertained if these findings represent aberrant actin expression of tumor cells or crossreactivity of antiactin antibodies. MSA has also been observed in the cells of the capsule of the liver, kidney and spleen and in decidual cells, some stromal cells of chorionic villi and the so-called fibroblastic reticulum cells of lymph nodes and spleens.
Applications
The increased sensitivity and specificity of newer monoclonal antibodies allow the use of anti-MSA antibodies in the identification of pleomorphic spindle cell tumors. Because of varying sensitivities, it is best to employ MSA with other myogenic markers such as smooth muscle actin and desmin when examining tumors, which potentially confuse with rhabdomyosarcoma (RMS), leiomyosarcoma (LMS) and myofibroblastic tumors (Azumi et al, 1988). Much of the current controversy as to which of these markers is the most sensitive for myogenic differentiation stems from the fact that the expression of the individual markers varies with the site of origin of the tumor (Rangdaeng & Truong, 1991). For example, most soft tissue and uterine LMS contain predominantlya- smooth muscle actin but those from the gastrointestinal tract show onlyb and g non-muscle actins and would thus be negative for HHF35. Myofibroblasts show heterogeneous immunophenotype and may be positive for vimentin only; for vimentin and a- smooth muscle actin; for vimentin and desmin; or for vimentin, desmin anda- smooth muscle actin (Skalli et al, 1989). Myofibroblastic proliferations such as nodular fasciitis may display characteristic peripheral/subplasmalemmal staining for muscle actin, yielding a ''tram track" appearance (Leong & Gown, 1993). Increased expression of MSA has been correlated with mesangial cell injury and proliferation in both rats and humans and can be employed as a marker of mesangial cell injury, activation and proliferation (Alpers et al, 1992).
Comments
Zenker's fixative appears to cause a marked decrease in the intensity of MSA staining. HIER enhances immunostaining and simple heating in distilled water at 60 C overnight or in ZnSO4 at 90 C for 10 min produces the best results. False-positive reactivity with clones HHF35 and 1A4 has been reported in non-Hodgkin's lymphoma, a problem attributed to contaminating antibodies, partial antibody degradation or excess antibody concentration which may occur with ascitic fluid preparations of anti-MSA (Sheehan & O'Brian, 1995). The problem was not observed in tissue culture supernatant antibodies and was abolished by the addition of 50 mmol/l of EDTA to the prediluted antibody.
References
•Alpers CE, Hudkins KL, Gown AM, Johnson RJ 1992. Enhanced expression of "muscle-specific" actin in glomerulonephritis. Kidney International 41: 1134-1142.
•Azumi N, Ben-Erza J, Battifora H 1988. Immunophenotypic diagnosis of leiomyosarcomas and rhabdomyosarcomas with monoclonal antibodies to muscle specific actin and desmin in formalin-fixed tissue. Modern Pathology 1: 469-474.
•Dervan PA, Tobbia IN 1989, Casey M, et al. Glomus tumors: an immunohistochemical profile of 11 cases. Histopathology 14: 483-491.
•Kung IT, Thallas V 1995, Spencer EJ, Wilson SM. Expression of muscle actins in diffuse mesotheliomas. Human Pathology 26: 565-570.
•Leong AS-Y, Gown AM 1993. Immunohistochemistry of "solid" tumours: poorly differentiated round cell and spindle cell tumors I. In: Leong AS-Y (ed). Applied Immunohistochemistry for surgical pathologists. London: Edward Arnold, pp24 72.
•Rangdaeng S, Truong LD 1991. Comparative immunohistochemical staining for desmin and muscle specific actin. A study of 576 cases. American Journal of Clinical Pathology 96: 32-45.
•Sheehan M, O'Brian DS 1995. False-positive immunoreactivity with muscle-specific actins in non-Hodgkin's lymphoma. Archives of Pathology and Laboratory Medicine 119: 225-228.
•Skalli O, Schurch W, Seemeyer TA et al 1989. Myofibroblasts from diverse pathologic settings are heterogenous in their content of actin isoforms and intermediate filament protein. Laboratory Investigation 60: 275-285.
•Tsukada T, Tippens D, Gordon D et al 1987. HHF35, a muscle-specific actin-specific monoclonal antibody. I. Immunocytochemical and biochemical characterisation. American Journal of Pathology 126: 51-60.
Bibliografia
Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.
