Lectins are carbohydrate-binding proteins of non-immune origin. They are essential components of plant active substances used by the plant in its system of defense and symbiotic interactions. It is expected that there is a relation between immunomodulatory activity of the protein extract and its content of lectin. In this study, we are aiming to explore the relation between the lectin content and the immunomodulatory activity using the erythroagglutination test of a group of immunomodulating protein plant extracts previously evaluated. The result shows that there is no relationship between the immunostimulatory activity and the presence or absence of lectins; lectins are not always immunostimulatory compounds; and they can also depressed immune activity. The erythro-agglutination is found qualitatively and quantitatively depending on the nature of lectin and its concentration in the protein extracted. Therefore, the lectin immunostimulatory effects found can also be used with an adjuvant effect in vaccine development; while, the lectin immunoinhibitory effects can be used in the cancer therapy.