15 min read 
Classification of Immunodiffusion The process of immuno-diffusion allows the determination or detection of antigens and antibodies through their precipitation that involves diffusion through a substance, such as gel agarose or agar. Simply, it denotes precipitation in a gel. It’s one of the many methods to create a precipitate from an antibody and a specific antigen. … Read more
17 min read 
What is Complement Fixation? Principle of Complement Fixation Test The principle of the complement fixation test is based on the interaction between antigens, antibodies, and complement proteins. When an antigen and antibody come into contact, they form an antigen-antibody (Ag-Ab) complex. This complex then interacts with complement proteins and becomes fixed with them. As a … Read more
4 min read 
Such is the case with the slide and tube Widal test. The agglutinins against the ‘0’ (somatic) and ‘H’ (flagellar) antigens of Salmonella typhi, paratyphi A, and paratyphi B are measured qualitatively (slide test) and quantitatively (Tube test) using a suspension of suitable organisms that have been killed. Widal-quantitative tube agglutination test This test aids … Read more
25 min read 
What is Hemagglutination assay? Haemagglutination Test Principle The fundamental principle underlying the hemagglutination test revolves around the interaction between antigens and antibodies present on the surface of Red Blood Cells (RBCs). When these antigens encounter their corresponding complementary antibodies or vice versa, they bind together, resulting in the agglutination or clumping of the RBCs. This … Read more
5 min read 
The nucleic acids of many viruses encode surface proteins (such as hemagglutinin (HA) of influenza virus) that agglutinate red blood cells (RBC) of numerous species. Hemagglutination is the process by which viral hemagglutinins react with red blood cells to form a lattice of agglutinated cells that settle unevenly in a tube or microtiter well. Unagglutinated … Read more
14 min read 
What is Anion Exchange Chromatography? Principle of Anion Exchange Chromatography The principle of anion exchange chromatography is based on the net surface charge of proteins, which changes with the pH and is determined by their isoelectric point (pI). The pI of a protein is the pH at which it carries no net charge. Below the … Read more
13 min read 
What is Cation Exchange Chromatography? Cation Exchange Chromatography Principles The principles of cation exchange chromatography are based on the net surface charge of proteins and the concept of isoelectric point (pI). The net surface charge of a protein can change with the pH of the surrounding environment. The pI of a protein refers to the … Read more
12 min read 
What is Sandwich ELISA? Sandwich ELISA Principle The principle of sandwich ELISA involves the detection of antigens using a combination of specific antibodies. The test begins by coating and immobilizing a known antibody onto the wells of a microtiter plate. This immobilized antibody serves as the capture antibody, which will bind to the antigen of … Read more
25 min read 
What is Direct ELISA? Principle of Direct ELISA The principle of direct ELISA revolves around the specific binding interaction between an antigen and its corresponding antibody. In this type of ELISA, the antigen of interest is adsorbed or immobilized onto the surface of a plastic plate, typically a microtiter plate with multiple wells. To minimize … Read more
24 min read 
What is Competitive ELISA? Principle of Competitive ELISA The principle of competitive ELISA is based on the competitive binding process that occurs between two specific antibodies and an antigen of interest. In this assay, two antibodies are utilized: one is conjugated with an enzyme, and the other is present in the test serum (if the … Read more