Cell-mediated immunity in rats injected with an antimalaria T-cell line

Host Resistance Assays

The goal of immunotoxicity testing is to obtain data useful for immunotoxicity safety assessment. Guidance in the performance of immunotoxicity safety evaluations is provided in documents from the US EPA for chemicals and the ICH S8 document for pharmaceuticals. The ICH S8 document outlines a tiered approach that includes (1) standard toxicity studies with associated hematology, immune system organ weights, and histopathology data; (2) functional assays, such as cytotoxic T lymphocyte (CTL) assays, natural killer (NK) cell assays, respiratory burst, phagocytosis, and T-cell-dependent antibody response (TDAR) assays; and (3) host resistance assays. Host resistance assays are considered the gold standard in immunotoxicity testing and provide a critical overview of the extent to which innate, adaptive, and homeostatic regulatory immune functions are integrated to protect the host. Both comprehensive and targeted host resistance assays are available, each with distinct advantages. This chapter serves to provide a general overview of the various assays that may be used, as well as a summary of procedures.

Protective CD4+ T-cell lines raised against Plasmodium chabaudi show characteristics of either Th1 or Th2 cells

Splenic T-lymphocyte lines were established in vitro from Plasmodium chabaudi-infected NIH mice on days 16 and 20 of a primary infection, and from mice after two or three infections. Each line responded specifically to stimulation with a lysed soluble extract of P. chabaudi-infected erythrocytes (pRBC), and displayed a CD4+ (L3T4+) surface phenotype. Both the day 16 and 20 cell lines, when stimulated in vitro, secreted interleukin-2 (IL-2) and gamma-interferon (IFN-gamma), indicative of their belonging to the T helper 1 (Th1) CD4+ subset. In contrast, both lines derived from reinfected mice secreted interleukin-4 (IL-4) and provided helper activity in antibody production to P. chabaudi in vitro, and thereby had the characteristics of Th2 cells. All four T-cell lines provided significant protection to naïve mice infected with P. chabaudi. In immunocompromised mice, the day 16 T-cell line was as protective as in naïve mice whereas the cell line from mice infected twice required the additional transfer of mature naïve splenic B cells to provide protection comparable to that seen in the immunocompetent naïve recipients. The results establish that protective immunity to P. chabaudi may be associated with the induction of CD4+ T cells of either the Th1 or Th2 subset which confer protection against this malaria parasite by mechanisms independent of, and dependent upon, B-cell involvement, respectively.

Cell-mediated immunity caused by beryllium compounds

Cells of spleen and lymph nodes were obtained from mice subcutaneously injected with BeCl2 once a week over a 6-week period. These cells were washed twice in cold phosphate-buffered saline and suspended at a final concentration of 2 x 10(7) cells in 1 ml of buffer. Subsequently, 0.5 ml of the suspension was injected into normal mice intravenously (passive transfer). The findings of the experiments using these mice are summarized as follows: (1) The footpad reaction test was performed 24 hrs after passive transfer. The mice receiving spleen cells or lymph node cells from mice sensitized with BeCl2 developed significant footpad swelling 24 and 48 hrs after challenge of BeCl2 as the antigen. (2) After passive transfer with sensitized spleen cells or lymph node cells the ears of the mice were painted with 7% BeCl2 in ethyl alcohol. Ears of these mice showed significant swelling as compared with those of controls. (3) The migration of peritoneal cells from mice receiving spleen or lymph node cells from sensitized mice was inhibited when tested in medium containing the antigen of BeCl2. From our present experiments, it was suggested that the beryllium sensitizing ability was related to active as well as passive cell-mediated immunity.

An arthritogenic lymphokine in the rat

A type II collagen-specific arthritogenic lymphokine has been identified in the rat. Arthritogenic factor (AF) is a 65 kD protein generated in vitro by T cells from rats with collagen arthritis, and it induces an erosive, proliferative synovitis when injected into the knee joint of syngeneic naive recipients. Complement does not appear to be required. These data identify a potential T cell-mediated effector mechanism in this model, and suggest that AF may function in other inflammatory synovial diseases.