Immunologic Reactions with Tobacco Mosaic Virus

1. Antisera were produced, separately, in rabbits to normal sap from healthy Turkish tobacco plants and to irus-sap from tobacco plants, affected with mosaic disease. 2. The immunologic reactions of the antisera were studied by means of: (a) Alexin-fixation tests. (b) Precipitation experiments, including: Precipitin-absorption tests with the same tobacco virus multiplied in tobacco, tomato, pepper, and petunia plants. (c) Experiments with the inactivation properties of both antisera and normal serum on virus-sap. 3. From the results obtained from the above experiments, the following conclusions were drawn: (a) Normal-tobacco-sap and virus-tobacco-sap possess antigenic substances in common. (b) Normal sap and virus-sap of tomato, pepper, and petunia plants contain antigenic substances in common with normal sap of tobacco. (c) Virus-saps of tomato, pepper, and petunia plants, have antigenic substances in common with virus-sap of tobacco, that are either not present in the normal tobacco sap or present only in small amounts. (d) The two antisera possess alexin-fixing antibodies and precipitins in common. (e) All of the precipitins to normal tobacco sap may be removed from either antiserum by absorption with virus-sap of tobacco. (f) Specific precipitins for virus-sap of tobacco, tomato, pepper, and petunia are present in the antiserum to tobacco virus-sap and cannot be removed by complete absorption with normal sap of tobacco. (g) Antiserum to virus-sap of tobacco, when used in an appropriate amount, has the power of completely inactivating virus-sap. A corresponding quantity of antiserum to normal tobacco sap, or normal rabbit or guinea-pig serum, does not exhibit the same preventive action on virus-sap. (h) There is some evidence that a specific antibody to virus-sap, lytic in nature, is present in the homologous antiserum.