Agglutination of antibody coated human erythrocytes has been found to depend on the zeta‐poten‐tial at the surface of shear and the dimensions of the antibody molecules. The critical zeta‐potential above which agglutination cannot occur has been shown to be —23 millivolts and —13 millivolts for saline and albumin antibodies respectively. A zeta‐potential below —18 millivolts for 19S molecules and below —8 millivolts for 7S molecules has been found to be necessary to give optimum agglutination and titer.
The value of the enzymes used in blood group serology has been shown to be related to their ability to reduce the net surface charge density with a consequent reduction in zeta. It is postulated that this effect is due to esterase rather than protease activity.
Bovine albumin and three synthetic polymers were found to bring about agglutination by reducing the zeta‐potential as a result of raising the dielectric constant. No evidence was found to support the hypothesis that they reduce the surface charge of the erythrocytes.
A satisfactory equation for calculating zeta, that can be used to predict the course of a serological reaction, has been computed from a determined value of —3190 esu/cm2 for the net surface charge density of human erythrocytes in NaCl‐buffer at 25 C. This has been extended to include electrolytes of other valences by taking into account the mean activity coefficient of the electrolyte. Evidence is presented to show that the minimum zeta associated with erythrocyte stability is about —7 millivolts. This was considered to be the minimum potential required to overcome the cohesive forces of interfacial tension.
In reaction mixtures imparting a zeta‐potential of —7 millivolts, tests with ten anti‐K and ten anti‐Fya sera show them to react similarly to anti‐D. There was no evidence to support the claim that these antibodies are monovalent.
An anti‐Rh gamma2‐globulin antibody preparation has been developed which can be administered intramuscularly and appears to be both safe and effective in the prevention of experimental Rh sensitization. Nine unsensitized Rh‐negative male volunteers were challenged once a month for five successive months with intravenous injections of 2 ml. of Rh‐positive blood. Four of these nine volunteers were passively protected each month with intramuscular injections of 5 ml. of this antibody preparation, administered 24 hours prior to the antigenic challenge. Three months after the last injection the passively acquired Rh antibodies were no longer demonstrable (by either the saline or indirect antiglobulin technics) in any of the four protected subjects and there was no sign of active antibody production six months after the last injection, whereas four of the five controls were all strongly sensitized.
The results on the use of gammaG-immunoglobulin to Rh factor for the prevention of active immunization of Rh-negative mothers at risk appear most promising. One hundred and seven mothers in the clinical trial have been followed for periods of about 6 months to 1(1/2)12 years after delivery. Of these, 48 were treated mothers who received 5 ml gammaG-immunoglobulin to Rh, and 59 were untreated mothers. Of the 48 treated mothers none are actively immunized; seven of the 59 control mothers have become actively immunized to Rh.
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