MABE1141-100UG Sigma-AldrichAnti-CD3D (TCR δ) Antibody, clone 5A6.E9

Mechanistic studies contribute greatly to our understanding of γδ T cell (γδTc) biology, aiding development of these cells as immunotherapeutic agents. The antibody blocking assay is an accepted method to determine the receptors involved in γδTc killing of tumor targets. Effectors and/or targets are preincubated with microgram quantities of monoclonal antibodies (mAb), often described by commercial sources to be useful for blocking assays. We and others have used such assays extensively in the past, correlating decreases in cytotoxicity against specific targets with involvement of the blocked receptor(s). However, we wondered whether other mechanisms might be at play beyond cytotoxicity inhibition. Indeed, administration of certain "blocking" mAb to the γδ T cell antigen receptor (γδTCR) induced γδTc death. Upon further investigation, we discovered that γδTc underwent apoptosis triggered by incubation with mAb to the γδTCR. This effect was specific, as no apoptosis was observed when αβ T cells (αβTc) were incubated with these mAb. Apoptosis was further potentiated by the presence of interleukin (IL)-2, often included in cytotoxicity assays; however, exogenous interleukin-2 (IL-2) did not contribute significantly to γδTc cytotoxicity against breast cancer cell lines. Here, we have investigated the usefulness of four mAb for use in blocking assays by assessing blocking properties in conjunction with their propensity to induce apoptosis in cultured primary human γδTc. We found that the 5A6.E9 clone was usually a better alternative to the commonly used B1 (or B1.1) and 11F2 clones; however, some variability in susceptibility to apoptosis induction was observed among donor cultures. Thus, viability assessment of primary effector cells treated with mAb alone should be undertaken in parallel with cytotoxicity assays employing blocking antibodies, to account for cytotoxicity reduction caused by effector cell death. Previous findings should be reassessed in this light.

The yellow fever 17D (YF-17D) vaccine is one of the most efficacious vaccines developed to date. Interestingly, vaccination with YF-17D induces IFN-γ production early after vaccination (days 5-7) before the development of classical antigen-specific CD8(+) and CD4(+) T cell responses. Here we investigated the cellular source of this early IFN-γ production. At days 5 and 7 post-vaccination activated CD8(+) gamma-delta TCR T cells produced IFN-γ and TNF-α. Activated CD4(+) T cells produced IFN-γ and TNF-α at day 7 post-vaccination. This early IFN-γ production was also induced after vaccination with recombinant YF-17D (rYF-17D), but was not observed after recombinant Adenovirus type 5 (rAd5) vaccination. Early IFN-γ production, therefore, might be an important aspect of yellow fever vaccination.

In 22 histologic cases of subcutaneous panniculitis-like lymphoma, we studied the clinicopathologic differences between CD56- and CD56+ cases (11 each). CD56- cases had skin ulcers (1 [9%]); tumor invasion in the superficial dermis (1 [9%]); erythrophagocytosis (10 [91%]); and medium-sized (11 [100%]), CD8+ (10 [91%]), T-cell receptor (TcR)betaF1+ (10 [91%]), and CD95 (Fas)- tumor cells. CD56+ cases had skin ulcers (9 [82%]); tumor invasion in the superficial dermis (8 [73%]); erythrophagocytosis (1 [9%]); and pleomorphic large (10 [91%]), CD8+ (2/10 [20%]), TcRbetaF1 + (3/10 [30%]), and CD95 (Fas)+ (7/10 [70%]) tumor cells. These 7 factors were significantly different between groups (P < .01). Median survival rates were 96 and 12 months for the CD56- and CD56+ groups, respectively. Age younger than 40 years, no skin ulcers, no tumor invasion in the superficial dermis, and CD8+, TcRbetaF1 +, CD95 (Fas)-, and CD56- tumor cells were significantly better prognostic factors (P < .01). The CD56- and CD56+ groups showed different tumor cell characteristics, clinicopathologic findings, and prognosis. In the CD56+ group, 1 was gamma/delta T-cell phenotype, 3 were alpha/beta T-cell, and 6 were TcRbetaF1- and gamma/delta- NK/T-cell, and 3 NK/T-cell cases had nuclear signals of Epstein-Barr virus-encoded RNA. Cases of CD56+ T- and NK/T-cell lymphoma had similar clinicopathologic findings and prognosis.

Campylobacter jejuni is currently the prime cause of food-borne bacterial gastro-enteritis. An important complication of C. jejuni enteritis is Guillain-Barré syndrome (GBS), an immune-mediated disorder of peripheral nerve tissue. Because little is known about T cell reactivity to C. jejuni, we have analyzed the in vitro immune response of normal individuals against five isolates of C. jejuni representing five different serotypes. We found a preferential expansion of peripheral blood gammadelta T cells after exposure to crude sonicates of all five C. jejuni serotypes. Expansion of gammadelta T cells was dependent on the presence of CD4+/alphabeta+ T cells in the cultures or addition of exogenous IL-2 or IL-15. C. jejuni stimulation was mediated via the TCR and appeared to be induced by a non-proteinaceous bacterial antigen, most likely of phosphoantigenic origin.