Characterization of the Antibody Response

1AJBORATORY EVALUATION of the J efficacy of typhoid vaccine has generally produced results which show little correlation with those obtained in field-trial evaluation. Hence, extensive field trials have been deemed necessary to evaluate the various typhoid vaccines {1-S). Recent advances in immunological methodology have demonstrated distinct classes of immunoglobulins with differing bio¬ logical activities (4). The application of these techniques has resulted in the detection of patients with immunoglobulin deficiencies who can produce normal levels of gamma M antibody but who cannot synthesize gamma G antibody (5). These patients are extremely susceptible to various bacterial infections, a sensitivity suggesting that while gamma M antibody is able to agglutinate with antigen in the laboratory, it is unable to protect against infection.