Underwood P A
Infect Immun. 1980 Feb;27(2):397-404. doi: 10.1128/iai.27.2.397-404.1980.
Reciprocal hemagglutination inhibition titrations were carried out with viruses and antisera of eight field strains of the A3 subtype of influenza A, covering the period from 1968 to 1975. The earlier strains (1968 through 1972) showed asymmetric cross-reactions, with antisera exhibiting more cross-reactions with antecedent strains than with subsequent ones. The later strains, although all were asymmetrically cross-reactive with earlier strains, tended to exhibit distant and variable cross-reactions with each other. The numbers and average affinities of antibody molecules capable of taking part in cross-reactions were calculated from equilibrium filtration experiments. It was found that all the antibody molecules in sera raised against the late strains could combine with earlier viruses, but with reduced affinity. Conversely, only a subset of the antibody molecules in sera raised against early strains could combine with later viruses. The results are discussed in the light of different theories concerning the nature and number of antigenic determinants on the hemagglutinin molecule. They support the existence of a single antigenic area to which all antibody molecules are directed, with differing affinities, rather than the existence of both "common" and "specific" determinants. Thermodynamic measurements on the homologous antigen-antibody reactions indicated that combination was mostly entropy driven. This suggested hydrophobic interaction as the mechanism of combination, i.e., that the complementary regions of antigen and antibody were made up largely or entirely of amino acids with hydrophobic side chains. There was no statistical difference in the magnitude of the entropy term (i.e., the average firmness of binding) among the different virus strains.
对1968年至1975年期间甲型流感A3亚型的8个野外分离株的病毒和抗血清进行了双向血凝抑制滴定。早期分离株（1968年至1972年）表现出不对称的交叉反应，抗血清与先前的分离株交叉反应比与后续的分离株更多。后期分离株虽然与早期分离株均表现出不对称交叉反应，但它们彼此之间倾向于表现出远距离和可变的交叉反应。通过平衡过滤实验计算能够参与交叉反应的抗体分子的数量和平均亲和力。结果发现，针对后期分离株产生的血清中的所有抗体分子都能与早期病毒结合，但亲和力降低。相反，针对早期分离株产生的血清中只有一部分抗体分子能与后期病毒结合。根据有关血凝素分子上抗原决定簇的性质和数量的不同理论对结果进行了讨论。这些结果支持存在一个所有抗体分子都针对的单一抗原区域，只是亲和力不同，而不是存在“共同”和“特异性”决定簇。对同源抗原-抗体反应的热力学测量表明，结合主要是由熵驱动的。这表明疏水相互作用是结合的机制，即抗原和抗体的互补区域主要或完全由具有疏水侧链的氨基酸组成。不同病毒株之间熵项的大小（即结合的平均牢固程度）没有统计学差异。
