In vitro quantification of cross-reactivity between beta-lactam antibiotics and anti-benzylpenicillin antibodies.

The phenomenon of cross-reactivity between allergens and anti-antibodies is believed to be a major factor underlying the incidence of immunologically mediated adverse reactions. A sensitive reproducible competitive enzyme-linked immunosorbent assay (ELISA) has been developed for the quantitative determination of the extent of cross-reactivity occurring between native beta-lactam antibiotics and anti-benzylpenicillin serum antibodies (anti-BPAbs) raised in presensitized rabbit serum in which free native antibiotic at a concentration of 3 mm, and benzylpenicillin cytochrome c (BPCC) adsorbed onto a solid surface, compete to bind free anti-BPAbs. The extent of BPPC-anti-BPAb binding is determined spectrophotometrically, following the addition of enzyme-labelled antispecies antiglobulin and a suitable substrate. The assay has been used to determine the levels of cross-reactivity exhibited by 29 commercially available beta-lactam antibiotics (14 penicillins and 15 cephalosporins), with results attained ranging for the penicillins between 9.1 and 100% and for the cephalosporins from 0.0 to 19.9%. The results thus indicate that cross-reactivity between different beta-lactams and anti-BPAbs does occur in vitro and that different beta-lactams cross-react to different extents, with cephalosporins cross-reacting less than the penicillins.

Differential suppression of experimental allergic diseases in rats infected with trypanosomes.

PVG/c rats, infected 3 days previously with 10(3) Trypanosoma brucei brucei S.42 organisms failed to develop adjuvant disease in response to an intradermal inoculation of mycobacterial adjuvant. By contrast, similarly infected rats, immunized with heterologous brain and spinal cord in Freund's complete adjuvant with pertussis vaccine as a secondary adjuvant, developed clinical signs of allergic encephalomyelitis (EAE) at least as severe as those in uninfected rats. Delayed hypersensitivity reactions to PPD were depressed in trypanosome-infected, adjuvant-injected rats, as were the reactions to myelin basic protein in infected rats developing EAE. There appeared to be no cross-reactivity between trypanosomal antigen and myelin basic protein which could account for the lack of suppression of EAE. It is suggested that the different extent to which autoimmunity is involved in these two experimental allergic diseases may account for the differential suppressive activity of trypanosome infections upon them.

Resistance and susceptibility to the induction of rat adjuvant disease. Diverging susceptibility and severity achieved by selective breeding.

Rats selected for their ability to develop or resist adjuvant disease were used to establish 2 inbred lines of rat over 20 generations. A resistant line was rapidly established with almost 100% non-responsiveness by the sixth generation. A line showing 100% susceptibility was also established very rapidly but throughout the course of the breeding programme the severity continued to increase in intensity to a level considerably above that to be seen in strains normally considered to be high responders. At the thirteenth generation and beyond, the susceptible line showed a marked sex difference in the secondary lesions, females being more severely affected than the males. The 2 lines of rat were also tested for their ability to develop experimental allergic encephalomyelitis (EAE) in selected generations. There was no clear correlation between the 2 diseases although those animals developing the most severe adjuvant disease also had the most severe EAE.

Suppression of rat adjuvant disease by cyclophosphamide pretreatment: evidence for an antibody mediated component in the pathogenesis of the disease.

Cyclophosphamide (Cy), given intraperitoneally at a dose of 100 mg per kg body weight 3 days before adjuvant, was found to abolish the development of adjuvant disease in the PVG/c rat. This treatment, however, enhanced the delayed hypersensitivity responses to purified protein derivative of tuberculin (PPD) developed by these animals. Lower doses of Cy caused a partial inhibition of arthritis which was dose-related. When the time between giving Cy and the injection of adjuvant was increased, a gradual time-dependent recovery of the response was observed. The arthritic response was restored by the passive transfer of 7.6 x 10(7) to 1.5 x 10(8) normal syngeneic spleen cells, although the development of secondary lesions was delayed by 7-14 days. The response could also be restored by the transfer of small amounts of serum from arthritic, but not normal, rats. Large amounts of serum failed to restore the response. Additional evidence that pretreatment with Cy preferentially depleted the B lymphocytes was obtained by the histological examination of the lymphoid tissue. It was also shown that the primary antibody response to sheep erythrocytes was abolished by Cy, but that skin allograft rejection was unaffected. A partial inhibition of the acute inflammatory reaction to carrageenan was observed 3 days after giving Cy. It is suggested that the pathogenesis of adjuvant arthritis involves an immune complex-mediated phase, whihc initiates the joint lesions. Once these lesions have formed, cell-mediated immune mechanisms predominate in the development of the disease. It is not known whether the persistence of immune complexes is necessary to maintain the lesions.