In humans, mucosal stimulation, like in systemic immunization, results in a transientrnappearance of B-cells capable of spontaneously producing antibodies. These cells are cellsrnen rOlUe to their final destinations. They primarily go to the sites they were initiallyrnstimulated but also to other se lected effector sites within the common mucosal Immunernsystem. During the migration , they express specific su rface molecules that represent thernsequence of developmental events taking place in the cells. Using these phenotypic cellrnmarkers Bâ€¢cells have been divided into discrete populations that span the developmentalrnstages. On the basis of these phenotypic markers, the migratory Bâ€¢cells are sorted intornfunctional groups. To achieve this, a novel approach that combines immunomagnetic beadsrnwith ELIS POT was developed. This method was applied to characterize the phenotypes,rnactivation pattern and homing commitments of B-cells after oral (Cholera Toxin CT) andrnsystemic (Tetanus Toxoidâ€¢ IT) vaccination. Following its success in the known systems, CTrnand IT vaccines, it was used to describe immunity in ch ron ically infected patients withrndiseases such as leishmaniasis, tuberculosis and schistosomiasis, whose pathology involvesrnimmunological hypersensitivity reaction (DTH). This method was shown to be capable ofrndescribing the immune status of an infected individual in terms of the phenotype and functionrnof antibody secreting cells (ASC). The fact that the distinction could be made betweenrnmucosally and systemically activated B-cells by differential expression of homing receptorsrn(L-selection, CD44 and a4(37) is an additional tool to evaluate the contribution of Mucosalrnassociate Lymphoid tissue (MALT) in disease causation and modulation of the immunernsystem under natural infections. The comparison of mucosal immune responses followingrndifferent routes of immunization was facilitated by the development of the cellular di spe rsionrntechnique. The technique made the parallel analysis of cellular composition of lymphoidrnti ssue such as the tonsil feasible. Induction from oral , intra-nasal, tonsillar and rectal routesrnof immunizations were compared . The intra-tonsillar and intra-nasal routes of immunizationsrnwere found to be capable of acting as induction sites for local and distant 8-cell responses.rnThe peroral and parenteral immunization of activated B-cells into the circulation, intratonrnsillar vaccination is hi gh ly localized. In the study of schistosomiasis, the C019 surfacernrnmarker was used for functional characterization of the types of antigen specificrnimmunoglobulin sec reting cells. Acco rdingly , IgM > IgA > fgG secreting cells were found inrnthe infected, while the reverse was characteristic of the control group. IgM dominance inrnacutely infected individuals was statistically significant (Prn15 years) and in those with light infections while in those that are under 15 years of age,rnIgM secreting cells to be dominant. Attempt to use the tonsils as induction sets to therncommon mucosal immune system resulted in highly localized response making it lessrninteresting in this respect. Instead the intranasal route was found to be convenient to reachrndistantly related mucosal sites. In the immunological characterization of S. mansoni in thernBALB/c mice, it was shown that following mucosal immunization with CTBâ€¢Sm28GSTrnvaccine, parasite induced pathology, number of eggs and worms were reduced by more thanrn50%,84% and 66%, respectively. This strongly suggested a strategy for induction of antiâ€¢rninfectious and antiâ€¢inflammatory immune response which could lead to development of arnvaccineâ€¢mediated control measure. Such a strategy may be applicable not only tornschistosomiasis but also to other diseases such as leishmaniasis, leprosy, and tuberculosis,rnthat induce similar delayed type high resistivity (DTH) responses as an immunopathologicalrnmechanism. This work has improved the technique of assessing the effect of vaccines, andrnhas evaluated the means of delivery of antigens that induce either stimulation and/or tolerancernat systemic and mucosal levels. The technique is of a broader application to chronic diseasernwith similar immunologic responses on mechanisms of pathogenesis.