{'fraction_non_alphanumeric': 0.03548895899053628, 'fraction_numerical': 0.008675078864353312, 'mean_word_length': 5.100961538461538, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Enrichment of memory cells carrying receptors for a protein antigen (HSA). II. Improved enrichment technique, using BSA density gradient separation.

Mice primed to human serum albumin (HSA) by means of an HSA--sheep red cell conjugate, developed a high level of memory to HSA, with little concomitant antibody production ('pure priming'). The proportion of HSA-specific antigen-binding cells was determined in the spleens of the primed mice by means of a rosette technique, using an HSA-donkey red cell conjugate. The specificity of the rosette-forming cells (RFC) was confirmed by the ability of soluble HSA to inhibit rosette formation. Highly enriched rosette suspensions (up to 40-fold enrichment) were prepared by bovine serum albumin density gradient centrifugation. The enriched suspensions could transfer adoptively memory to HSA, whereas the rosette-depleted fractions were totally inactive. It was thus confirmed that memory cells are included in the antigen-binding cells. A detectable level of memory could be transferred with 3000 rosettes. RFC similarly isolated from spleens of non-primed mice could also transfer a low level of responsiveness to HSA, but only when large numbers (70,000) were injected, together with primed, RFC-depleted spleen cells.