tailieunhanh - Introduction to Medical Immunology - part 3

Tham khảo tài liệu 'introduction to medical immunology - part 3', y tế - sức khoẻ, y học thường thức phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Page 126 Figure Diagrammatic representation of the avidity concept. The binding of antigen molecules by several antibodies of different specificities A stabilizes the immune complex since it is highly unlikely that all Ag Ab reactions dissociate simultaneously at any given point of time B . Redrawn from Roitt I. Essential Immunology 4th ed. Blackwell Scientific Publications Oxford 1980. 1. Antisera containing polyclonal antibodies can often be found to cross-react with immunogens partially related to that used for immunization due to the existence of common epitopes or of epitopes with similar configurations. 2. Less frequently a cross-reaction may be totally unexpected involving totally unrelated antigens that happen to present epitopes whose whole spatial configuration may be similar enough to allow the cross-reaction. 3. The avidity of a cross-reaction depends on the degree of structural similarity between the shared epitopes when the avidity reaches a very low point the cross-reaction will no longer be detectable Fig. . 4. The differential avidity of given antiserum for the original immunogen and for other immunogens sharing epitopes of similar structure is responsible for the specificity of the antiserum . its ability to recognize only one single immunogen or a few very closely related immunogens . Figure Diagrammatic representation of the concept of cross-reaction between complex antigens. An antiserum containing several antibody populations to the determinants of a given antigen will react with other antigens sharing common or closely related determinants. The avidity of the reaction will decrease with decreasing structural closeness until it will no longer be detectable. The reactivity of the same antiserum with several related antigens is designated as a cross-reaction. Redrawn from Roitt I. Essential Immunology 4th ed. Blackwell Scientific Publications Oxford 1980. Page 127 II. Specific Types of Antigen-Antibody Reactions A. Precipitation.