The early phase of the immune response to live and killed [formula omitted] vaccines in sheep — Cellular and immunoglobulin parameters

Abstract

Various cellular and protein parameters in efferent lymph were monitored during early stages of immune responses in the draining popliteal lymph nodes of sheep following injection with either live or killed Staphylococcus aureus vaccines. Significantly higher outputs of leucocytes and lymphoblasts were measured in lymph from animals injected with the live vaccine (Group 1) compared with animals given the killed vaccine (Group 2) and non-immunised controls (Group 3). At 48 h post-injection the mean output of leucocytes in lymph for Group 1 was 9.5 × 10 7 cells/h, and for Groups 2 and 3 comparable mean outputs were 5.2 × 10 7 and 2.2 × 10 7 respectively. There was a marked increase in IgM-containing cells in Group 1 animals, significant differences between Group 1 and 2 occurring 96 h post-injection. A difference was observed between the two immunised groups in the kinetics of output of cells containing antibody to a staphylococcal antigen extract. There was a slower increase in antibody-containing cells for Group 1 than for Group 2 animals. The mean proportion of antibody-containing cells reached 0.09% (of total leucocytes) at 72 h post-injection for Group 2 and 0.10% at 120 h post-injection for Group 1. Rapid increases in flow rate of lymph were recorded in animals in Group 1. These results were in contrast to lower corresponding values observed in sheep in Groups 2 and 3. There was a twofold increase in the lymph: serum (L:S) concentration ratio for IgG2 in animals in Group 1 and the evidence suggested that this was due to local synthesis of IgG2 by lymphoid cells in the abscess at the site of injection and/or in the draining popliteal lymph node. This change in L:S ratio for IgG2 was not recorded for sheep in Groups 2 and 3.