Establishment and characterization of a T-cell line specific for Rickettsia tsutsugamushi

Abstract

To study the immunological protective system against rickettsial infection, a T-cell line specific for Rickettsia tsutsugamushi antigen was established by long-term culture of splenocytes from mice immunized with live Gilliam strain R. tsutsugamushi and then propagated in the presence of homologous rickettsial antigen and syngeneic filler cells. The characteristics of the T-cell line and its capacity to induce antirickettsial protection in vivo were studied. Flow cytometric analysis demonstrated that the T-cell line showed the phenotype Thy-1.2+ L3T4+ Lyt-2-, suggestive of helper T cells. In a lymphocyte proliferation assay, this cell line showed a specific response to Gilliam antigen, partial cross-reactivity to Karp antigen, but no response to Kato antigen. The proliferative response of this T-cell line was filler cell dependent, and genetic restriction was observed between the T-cell line and filler cells. The T-cell line produced gamma interferon, one of the macrophage-activating factors, in cultures with specific antigen and was able to adoptively mediate antirickettsial protection in vivo. The data presented here suggest that antigen-specific helper T cells play an important role in protection against rickettsial infection.

CD4+T-Lymphocyte and Immunoglobulin G2 Responses in Calves Immunized withAnaplasma marginaleOuter Membranes and Protected against Homologous Challenge

“…IFN-␥ is important for protection in mice infected with Rickettsia spp. (20,28,30) and activates macrophages to secrete oxygen and nitrogen intermediates, such as NO, that are inhibitory for many intracellular pathogens, including rickettsiae (31,49). Soluble factors released by PBMC obtained from cattle during acute A. marginale infection and cultured with specific antigen were toxic for intraerythrocytic A. marginale (58).…”

Induction of Protective Immunity Against Scrub Typhus With a 56-Kilodalton Recombinant Antigen Fused With a 47-Kilodalton Antigen of Orientia Tsutsugamushi Karp

“…Interferon-␥ and IL-2 are both the products of CD4 + T (Th1) cells, and IFN-␥ has been shown to inhibit rickettsial growth in vitro and is believed to play an important role in resistance to rickettsial infection in vivo. 10,35,37,38 Moreover, Th1 cells are capable of inducing DTH and activating macrophages, making these cells particularly suited to deal with intracellular organisms.…”

Effect of Rickettsial Antigen‐Specific T Cell Line on the Interaction of Rickettsia tsutsugamushi with Macrophages

“…1 and 2 indicate that rickettsial antigen-specific T cell line can produce a factor which acts on macrophages infected with R. tsutsugamushi cytotoxically and selectively, and suggest the presence of another rickettsicidal mechanism in macrophages infected with rickettsiae. Moreover, we have reported that a rickettsial antigen-specific T cell line is able to produce gamma-interferon antigen-specifically (5), and it has also been reported that gammainterferon inhibits rickettsial growth in nonphagocytic cells (8). It seems to be more efficient for these soluble factors, cytotoxic lymphocytes and activated macrophages to inhibit the growth of rickettsiae in the host cooperatively.…”