Multiple self epitopes on the Rhesus polypeptides stimulate immunologically ignorant human T cells in vitro

Abstract

The extent of autoreactive T cell repertoire in the normal individual has previously been unclear. Here we demonstrate that T cells from healthy humans can be stimulated by multiple epitopes on a self protein to give primary proliferative responses in vitro. Synthetic 15-mer peptides, corresponding to the sequence of a human red blood cell Rhesus polypeptide, were tested for the ability to stimulate normal T cells. Multiple peptides were found to provoke responses reproducibly, and the proliferation could be blocked consistently by antibodies to HLA-DR, but not -DP or -DQ. T cells from each donor proliferated in response to different patterns of peptides, but this variation in pattern was less marked in individuals with the same HLA-DR type. The responses were comparable in kinetics to those elicited by the non-recall foreign antigen keyhole limpet hemocyanin, and the responding cells are most commonly derived from the CD45RA+ subpopulation, indicating that they had not been activated in vivo. It is considered that T cells are "immunologically ignorant" of many self peptides, presumably because they correspond to cryptic epitopes that are not normally presented in vivo.

Identification, immunomodulatory activity, and immunogenicity of the major helper T-cell epitope on the K blood group antigen

“…PPD readily invokes recall T-cell responses in a high proportion of United Kingdom citizens 19 as most have been immunized with the Bacilli Calmette-Guérin vaccine.…”

“…The viability of the PBMCs was Ͼ 90%, as confirmed by trypan blue staining. As previously described, 13,[19][20][21] PBMCs were cultured at a final concentration of 1.25 ϫ 10 6 cells/mL in ␣ modification of Eagle medium (␣-MEM; Invitrogen) supplemented with 1% 2mM L-glutamine (Invitrogen), 2% 20mM HEPES buffer (Sigma-Aldrich), 2% penicillin streptomycin (Invitrogen), and 5% autologous sera. PBMCs were incubated with peptides or control stimuli for 5 days at 37°C in a humidified atmosphere of 5% CO 2 /95% air.…”

“…13,[19][20][21] The proliferation by the cells was recorded as mean cpm Ϯ SD of the triplicate samples, or as a stimulation index (SI) expressing the rate of mean cpm in stimulated versus unstimulated control cultures. An SI Ͼ 3 was interpreted as a proliferative response.…”

“…As described elsewhere, 13,19,20 to determine the HLA class II restriction of the cells responding in cultures, blocking Abs specific for HLA-DP/DQ/DR or HLA-DR (all from BD Biosciences) were added at a final concentration of 5 g/mL.…”

“…19,[21][22][23] Briefly, PBMCs were incubated with murine mAb UCHL1 (specific for human CD45RO) or SN130 (specific for human CD45RA; gifts from Profs P. C. L. Beverley (University College London, London, United Kingdom) and G. Janossy (Royal Free Hospital, London, United Kingdom). Cells that bound mAb were removed by immunomagnetic separation using ferrous beads coated with Ab specific for mouse IgG (Biomag; PerSeptive Biosystems).…”