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Differentiation Between Two Formae Speciales of Fusarium oxysporum by Antisera Produced in Mice Immunologically Tolerized at Birth Through Lactation. G. Del Sorbo, Institute of Plant Pathology, Via Università 100, 80055 Portici (NA), ITALY; F. Scala(2), R. Capparelli(3), D. Iannelli(4), and C. Noviello(5). (2)(5)Institute of Plant Pathology, Via Università 100, 80055 Portici (NA), ITALY; (3)(4)Department of Animal Production, Via Università 100, 80055 Portici (NA), ITALY. Phytopathology 83:1178-1182. Accepted for publication 27 April 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-1178.

The immunological tolerance technique was used to produce antisera able to differentiate between two formae speciales (lycopersici and dianthi) of Fusarium oxysporum. Induction of tolerance was obtained in C57BL/6 mice that at birth received soluble mycelial extract through lactation. Offspring of mothers injected intravenously within 12 h after delivery with 1 mg of protein of F. oxysporum f. sp. lycopersici extract, isolate 1110, were immunized with the extract (100 μg of protein) of F. oxysporum f. sp. dianthi, isolate 1111, 28, 35, 42, and 49 days after birth. Similarly, offspring of mothers injected with F. o. dianthi, isolate 1111, were immunized with F. o. lycopersici, isolate 1110. In both cases, antisera collected at 56 days of age clearly distinguished between the two formae by immuno-radiometric assay and Western blotting. Differentiation was not possible with antisera collected from mice not exposed to the antigen at birth. Tolerization was short-lived because antisera collected from tolerized mice at 88 days could no longer discriminate between the two formae. Further, it was shown that the strain of mice, route of antigen administration, and form and doses of antigen all influence the induction of tolerance. Tolerance was induced in the C57BL/6 strain of mice but not in the BALB/c strain. No tolerizing effect was observed when the antigen was administered intraperitoneally to newborn mice or when a particulate antigen (spores) replaced the soluble extract. The technique proved useful for targeting the immune response toward fungal antigens of interest and for revealing fine antigenic differences between serologically and taxonomically related entities.