Molecular Bases of Protein Antigenicity and Determinants of Immunogenicity, Anergy, and Mitogenicity.

BACKGROUND: The immune system is able to recognize substances that originate from inside or outside the body and are potentially harmful. Foreign substances that bind to immune system components exhibit antigenicity and are defined as antigens. The antigens exhibiting immunogenicity can induce innate or adaptive immune responses and give rise to humoral or cell-mediated immunity. The antigens exhibiting mitogenicity can cross-link cell membrane receptors on B and T lymphocytes leading to cell proliferation. All antigens vary greatly in physicochemical features such as biochemical nature, structural complexity, molecular size, foreignness, solubility, and so on. OBJECTIVE: Thus, this review aims to describe the molecular bases of protein-antigenicity and those molecular bases that lead to an immune response, lymphocyte proliferation, or unresponsiveness. CONCLUSION: The epitopes of an antigen are located in surface areas; they are about 880-3,300 Da in size. They are protein, carbohydrate, or lipid in nature. Soluble antigens are smaller than 1 nm and are endocytosed less efficiently than particulate antigens. The more the structural complexity of an antigen increases, the more the antigenicity increases due to the number and variety of epitopes. The smallest immunogens are about 4,000-10,000 Da in size. The more phylogenetically distant immunogens are from the immunogen-recipient, the more immunogenicity increases. Antigens that are immunogens can trigger an innate or adaptive immune response. The innate response is induced by antigens that are pathogen-associated molecular patterns. Exogenous antigens, T Dependent or T Independent, induce humoral immunogenicity. TD protein-antigens require two epitopes, one sequential and one conformational to induce antibodies, whereas, TI non-protein-antigens require only one conformational epitope to induce low-affinity antibodies. Endogenous protein antigens require only one sequential epitope to induce cell-mediated immunogenicity.

Tannic Acid, as a Structural Moiety Coupled to a Protein Antigen, Exhibiting a Molecular-structure Adjuvant Activity for Antibody Specificity Enhancement.

BACKGROUND: An antigen is a small foreign substance, such as a microorganism structural protein, that may trigger an immune response once inside the body. Antigens are preferentially used rather than completely attenuated microorganisms to develop safe vaccines. Unfortunately, not all antigens are able to induce an immune response. Thus, new adjuvants to enhance the antigen's ability to stimulate immunity must be developed. OBJECTIVES: Therefore, this work aimed to evaluate the molecular-structure adjuvant activity of tannic acid (TA) coupled to a protein antigen in Balb/c mice. METHODS: Bovine serum albumin (BSA) was used as an antigen. The coupling of BSA and TA was mediated by carbodiimide crosslinking, and verified by SDS-PAGE. Forty-two Balb/c mice were divided into seven groups, including two controls without antigen, an antigen control, an adjuvant control, and two treatment groups. An additional group was used for macrophages isolation. A 30-day scheme was used to immunize the mice. The analysis of humoral immunity included immunoglobulin quantification, isotyping and antigen-antibody precipitation. The analysis of cell-mediated immunity included the quantification of nitric oxide from peritoneal macrophages and splenocytes' proliferation assay after treatment stimulation. RESULTS: No differences were found in the antibodies' concentration or isotypes induced with the conjugate or the pure BSA. However, an immunogenicity improvement (p < 0.05) was observed through the specific anti-BSA antibody titers in mice immunized with the conjugate. Besides, macrophage activation (p < 0.05) was detected when stimulated with the treatments containing TA. CONCLUSION: Tannic acid exhibited macrophages' activation properties. Moreover, when TA was incorporated into the structure of a protein antigen, such as BSA, an antibody specificity enhancement was observed. This was a consequence of antigen processing by activated antigen-presenting cells. These results showed the use of tannic acid as a novel candidate for vaccine molecular-structure adjuvant.

EVALUATION OF THE CHELATING EFFECT OF METHANOLIC EXTRACT OF CORIANDRUM SATIVUM AND ITS FRACTIONS ON WISTAR RATS POISONED WITH LEAD ACETATE.

BACKGROUND: The rate of lead poisoning has decreased in recent years due to increased health control in industries that use this metal. However, it is still a public health problem worldwide. The use of various plants with chelating properties has been a topic of research today. In traditional medicine, it is said that Coriandrum sativum has chelating properties, but there is no scientific evidence to support this fact. The purpose of this research is to evaluate the chelating effect of methanol extract of coriander and its fractions on Wistar rats intoxicated with lead. MATERIALS AND METHODS: In this research, male Wistar rats were poisoned with 50 mg/kg of lead acetate and treated with 50 mg/kg of methanol extract and its fractions. The extract and its fractions were administered to four treatment groups. Positive and negative controls were established. Hemoglobin, hematocrit and lead concentrations were analyzed; liver was evaluated histologically in control and treatment groups. RESULTS: The methanol extract of coriander presented a LD50 >1000 mg/dL. The group administered with the methanol extract showed significant difference in the levels of hemoglobin and hematocrit compared to the negative control group. Lead concentration in treatment groups showed a decrease compared to the positive control. Histological evaluation of tissue showed less damage in groups administered with methanolic extract and its fractions compared to the positive control which presented structural alterations. CONCLUSION: Coriander extracts protect liver and lower lead concentration in rats intoxicated with lead in contrast to the positive control group.