Characterization of rat T-cell clones with bacterial specificity

We have isolated 10 rat T-cell clones from the spleen or lymph nodes of seven different donors. These rats were immunized with 2-5 x 10(8) killed Actinobacillus actinomycetemcomitans (Aa) bacteria, injected either subcutaneously (s.c.) in complete Freund's adjuvant or intraperitoneally (i.p.) in saline. Clones studied to date have demonstrated a T-helper (Th) phenotype W3/13+, W3/25+, OX8- and OX22-. Clones were not stimulated in vitro by purified Aa-lipopolysaccharide (LPS) or heterologous Gram-negative bacteria, but proliferated when stimulated by bacteria representative of each of the three serological groups of Actinobacillus, indicating specificity for an Actinobacillus-common antigen other than LPS. One clone (A4) proliferated vigorously when stimulated with concanavalin A (Con A) in vitro, produced interleukin-2 (IL-2) and was provisionally classified as a Th1 type. This appears to be one of the few Th1-type rat clones reported. All other clones tested did not produce IL-2, exhibited B-cell help to some extent, did not induce delayed-type hypersensitivity (DTH) when injected into the footpads of naive rats along with the specific antigen, and were classified as Th2 type. Adoptive transfer of 10(6) cells of one Th2-type Aa-specific clone into syngeneic recipients resulted in a specific splenocyte in vitro response to Aa 12-14 weeks after cell transfer, indicating survival of cloned cells in recipient animals. The use of such clones in studies of experimental periodontal disease is discussed.