Generation, maintenance and reactivity of ovine T-lymphocyte clones derived from sheep immunized with pili from Bacteroides nodosus

Abstract

Peripheral blood leucocytes (PBL) from sheep immunized with pilus protein purified from Bacteroides nodosus serogroup A were cultivated in vitro and cloned in the presence of the specific antigen and autologous antigen-presenting cells (APC). The efficiency of cloning was enhanced by high proliferative responses to pili during the initial week of cultivation, and the provision of recombinant human interleukin-2 (rec-IL-2). After three passages at weekly intervals, bulk cultures of PBL and cloned T-lymphocytes were greater than 99% CD4+, CD8-, sIg-, i.e. the characteristic phenotype of helper T-lymphocytes. Cloned T-lymphocytes were devoid of allo-reactivity, and were restricted by class II antigens of the major histocompatibility complex (MHC). Both bulk PBL and cloned T-lymphocytes exhibited similar patterns of reactivity against pili from different serogroups of B. nodosus and the T-lymphocytes reacted to three of six peptides synthesized from the amino-acid sequence of pilus from serogroup A. Although clones of T-lymphocytes could retain antigen specificity for up to 2 months of cultivation, several attempts to recover clones with specific reactivity after storage in liquid nitrogen were unsuccessful.