The stability of chemotherapeutic agents incorporated into agar plates was studied by comparison of minimum inhibitory concentrations on fresh and stored plates and by direct bioassay of the chemotherapeutic agar plates. Plates were stored in sealed bags at 4 C. No loss of bioactivity was demonstrated after 30 days of storage in plates containing methicillin, erythromycin, cephalothin, tetracycline, chloramphenicol, kanamycin, streptomycin, polymyxin B, or nalidixic acid. Penicillin G, ampicillin, and nitrofurantoin showed statistically significant losses of activity after 4 weeks. None of the chemotherapeutics tested showed significant loss in activity after 1 week.

Competition between proteins and other macromolecules for adsorption sites on plastic was studied with the enzyme-linked immunosorbent assay (ELISA) to determine effects of the use of antigenic mixtures or extracts of organisms on assays of antibodies and antigens by ELISA. A comparison of a number of different polystyrene microplates with bovine albumin and human immunoglobulin G (IgG) as antigens showed two major classes of plates: those which adsorbed albumin poorly and those which adsorbed albumin well. IgG adsorbed well on all plates, but plates which adsorbed albumin best also gave significant background levels of nonspecific binding of conjugate. When mixtures of IgG and bovine serum albumin were used as coating antigens, significant competition was observed; the component present at 1% or less in the mixture was essentially undetectable unless excessive amounts of conjugate were used. The important factor was the ratio of competitor to antigen, not the absolute amount. Other proteins (ovalbumin, rabbit albumin, human albumin, and gelatin) were equally effective competitors for adsorption sites on plastic. Nonionic detergents (Tween 20, and Triton X-100) were strong competitors even at 10:1 competitor-to-antigen ratios. In antigen capture assays, normal serum components blocked attachment of antigen-specific IgG, but this competition could be lessened to a degree by the use of strongly binding polystyrene plates. In indirect ELISA for measurement of serum antibody, the use of antigenic mixtures gave significantly lower antibody titers when the desired antigen was less than 1% of the total protein coated. Therefore, the use of mixed or crude antigens in ELISA presents significant problems concerning the sensitivity and specificity of tests. The enzyme-linked immunosorbent assay (ELISA) (9) is a major tool for detecting antigens and antibodies in a wide variety of diseases (20, 21). Although the method was initially devised for measurement of antibodies to individual proteins, a large number of assays for individual disease agents have been devised using partially purified or even unpurified antigens. Such assays are not uniformly successful, and when they are it is not possible to define the reacting antigen(s). If we were to wait until suitably purified antigens were available, a number of currently useful assays would not be available for serodiagnosis. It has been recognized that components of antigenic mixtures (i.e., an extract of a microorganism) likely compete with each other for the limited sites on plastic surfaces (4, 5, 13, 16). Thus, studies to determine the nature of competition are necessary to define conditions under which ELISAs can best be performed with partially purified or unpurified antigens. Proteins apparently attach to plastic surfaces by hydrophobic interactions (12, 19), and the

The stability of chemotherapeutic agents incorporated into agar plates was studied by comparison of minimum inhibitory concentrations on fresh and stored plates and by direct bioassay of the chemotherapeutic agar plates. Plates were stored in sealed bags at 4 C. No loss of bioactivity was demonstrated after 30 days of storage in plates containing methicillin, erythromycin, cephalothin, tetracycline, chloramphenicol, kanamycin, streptomycin, polymyxin B, or nalidixic acid. Penicillin G, ampicillin, and nitrofurantoin showed statistically significant losses of activity after 4 weeks. None of the chemotherapeutics tested showed significant loss in activity after 1 week.

Pulmonary infection with Pseudomonas aeruginosa (PA)eventually occurs in virtually every patient with cystic fibrosia. Progression of infection and, ultimately, death occurs despite circulating specific antibody. For these reasons, studies of cell mediaeed imune responses to PA were undertaken in patients with cystic fibrosis. In vitro lymphocyte proliferative responses to PA, Hemophilus influenzae, Streptococcus hemolyticus and Staphylococcus aureus antigen were tested by ' H thymidine incorporation. --Twenty-nine patients with chronic PA infection including 16 in fair or good condition (Shwachman Case Hiatory Score of 15-25 points) and 13 in poor condition (Score of 1-14) were tested. In addition, 6 patients who had never had PA recovered from sputum cultures and 13 normal persons were also tested. The mean response to three different PA strains was 753 counts per minute (cpm) in the "poor" group compared to 3234 cpm in the "good" group (pq0.0005) and 2572 in the normal groups (~~0.005). This difference was not present in the responses to PHA and Con-A or to the other bacterial antigens. Two terminally ill patients gave lower responses to four of their own PA strains than did the other patients. In addition, two sibling pairs in which onechild waa aeverely ill and infected with PA while the other child had not yet shown PA on sputum cultures were studied. In both cases, the uninfected child had normal responses, whereaae the severely ill siblinghadvirtually no response against his own PA. The addition of PHA to T-cell incubation caused an immediate four-fold stimulation of GU while non-T cells were totally unaffected (92+22 vs 196+20).Lactate production (LP) by enriched T-cells (s219) was k c h less than LP by non-T cells (351535) (p