Plants have an "immune system" although it is MUCH simpler than ours. SiRNAs are part of this response especially against RNA virus wich are common in plants, but this mechanism is also important in normal cell biology controling regulation of transcription and/or translation. Human diseases in plants wouldn´t work because they are completly different systems. The biology is totally different. But there are insights into pathogenicity mechanisms which can be drawn from plant pathogens. I think Bartonella causes a vascular disease which paralels with a plant disease or something like that. Seeya!! PLANT IMMUNITY friends, plants are also having the antibody like molecules called 'LECTINS', moreover these are also used in certain clinical diagnostic blood grouping reations where they will act non-specifically with human serum antigen. However the plants are not that much able to resist the outer environmental factors like nematodes, pests, plant pathogens etc. According to my belief, the declined immunity of the plants may be dur to the sudden environment changes like green house effect, air and water pollution etc., also another possibiilty is the fast evolutionary change in the infectious agents as compare to plant Nutritional Herbology When plants have the minerals they need, then they are able to produce chemicals such as volatile oils, saponins, tannins, etc. which protect them against insect damage and disease. These are also considered the "active components" of herbs. The fact that "medicinal" herbs contain higher percentages of these chemicals than ordinary foods suggests that these chemicals are essential to immune system function in human beings. The fact that they are produced as a part of the plant's immune system gives credence to the idea that plants with strong immune systems provide the nutrition that people and animals need for strong immune systems. These "medicinal" chemicals in our foods are also largely responsible for their characteristic taste and smell. Thus, plants which have good mineral content will have stronger odors and flavors than plants which do not. Just pick up the produce in the supermarket and smell it and you will discover how sickly the food is. If it were not being "protected" by chemical poisons, nature would destroy these sickly plants