FINE ANTIGEN-SPECIFICITY OF HUMAN GAMMA-DELTA T-CELL LINES (V-GAMMA-9-1) OF A GRAM-POSITIVE BACTERIUM, STREPTOCOCCUS-SANGUIS() ESTABLISHED BY REPETITIVE STIMULATION WITH A SEROTYPE (KTH)

We have established human gamma delta T cell lines specific for Strepr ococcus sanguis (S.sanguis) KTH-1 present in normal oral cavity flora. The CD4(-)CD8(-)CD3(+)V gamma 9(+)V delta 1(-)CD45RO(+)CD25(+) T cell lines showed a proliferative response to the streptococcal antigen (A g) in the presence of autologous antigen-presenting cells without appa rent evidence of HLA restriction. The proliferative response of the ga mma delta T cell lines was completely blocked by anti-TcR gamma delta monoclonal antibody (mAb) and anti-HLA class I mAb (W6/32),whereas ant i-HLA classical class Ia mAb (B-H9; anti-HLA-A,B,C), anti-HLA class II mAb (anti-DR, anti-DQ, and anti-DP) and anti-CD4 mAb did not have any inhibitory effects. Surprisingly, the gamma delta T cell lines showed the proliferative response against the original bacterial Ag KTH-1 ex clusively, and exhibited no cross-reactivity with nominal Ag such as p urified protein derivative of tuberculin, tetanus toxoid and Mycobacte rium tuberculosis, or the same species but different strain of S. sang uis, American Type Culture Collection (ATCC) standard strain (10556), or even with the same strain but different serotype of S. sanguis, KTH -3. Moreover, cytokine production of the gamma delta T cell lines was similar to the Th1 pattern [interferon-gamma, tumor necrosis factor (T NF)-alpha and TNF-beta]. They also produced interleukin-8 that functio ns as one of chemoattractants for polymorphonuclear cells. Using direc t sequencing technique of the polymerase chain reaction products, we f ound that junctional diversity of the T cell receptor (TcR) used by th e parental KTH-1 specific gamma delta T cell line and its subclones is rather limited. It is suggested that gamma delta T cells with canonic al TcR could preferentially respond to KTH-1 Ag. Thus, in addition to a broad or cross-reactivity of gamma delta T cells against phylogeneti cally conserved stress/heat-shock protein, which is well characterized by others, some peripheral blood gamma delta T cells could recognize and kill exogenous agents with fine antigenic specificity to protect t he body against them.