Induction and reversal of immune paralysis in vitro.

Induction of the immune response can only be completed after antigen is removed from the cellular environment. Primed rabbit lymph node fragments were cultured in vitro with 5 mg/ml BSA. If antigen was removed from the fragments 2 hr later, they produced a normal anti-BSA response, which was first evident 5 days later.

The X-Y-Z scheme of immunocyte maturation. VII. Cell division and the establishment of short-term IgM memory.

Short-term IgM memory is established within 1 day after primary injection. This 1 day priming is independent of cell division as it can take place in the pressence of methotrexate or hydroxyurea. The primary response involves a similar 1 day nonproliferative phase.

The X-Y-Z scheme of immunocyte maturation. V. Paralysis of memory cells.

A concentration of 5 mg/ml bovine serum albumin (BSA) prevents the in vitro elicitation of a secondary response in primed rabbit popliteal lymph nodes, if it is left in contact with the node fragments for the first 6 days of culture. No antibody formation can be detected at any time during the culture period in most cases, although occasional fragments are resistant to inhibition. Reducing the exposure time to the first 3 days of culture delays the peak of the antibody response.

High-dose delay of the immune response. Effect of actinomycin D on continuation of the immune response in vitro.

The continuation of the primary and secondary antibody response to human serum albumin (HSA), induced in vivo, was followed in explanted chicken spleen fragments. The effect of actinomycin D (AMD) on the in vitro response was studied in spleens from chickens injected with various doses of HSA and removed at differing intervals after injection. The antibody response of "early spleen" cultures was AMD-sensitive, while cultures of spleens removed later were AMD-resistant.

Antigen binding to cells: determination by enzymic fluorogenic group hydrolysis.

A sensitive method for detecting cells containing antibody to beta-galactosidase has been devised. The enzyme attached to the cells containing antibody can hydrolyze a fluorogenic substrate and yield fluorescent products which are measured microphotofluorometrically. This method of detecting a few molecules of antibody is applicable to other enzyme antigen systems.

The X-Y-Z scheme of immunocyte maturation. IV. The exhaustion of memory cells.

A set of conditions has been described under which primed rabbit lymph nodes produce a secondary antibody response upon in vivo stimulation with a large dose of antigen, but are subsequently "exhausted;" that is, lymph node cultures prepared at intervals following the booster injection cannot be re-stimulated to display tertiary responses. Rabbits given 100-fold less antigen in the booster inoculum were able to give a tertiary response upon in vitro challenge. The system used permits neither induction nor continuation of a primary response to BSA in vitro.