Site of initiation of the plasma cell reaction in the rabbit lymph node. Ultrastructural evidence for two distinct antibody forming cell precursors.

This research involved studying the initiation of the plasma cell reaction in the lymph nodes of rabbits by creating a model in which the T-cell population was depleted. This was achieved by twice exposing the rabbits to sublethal total body-X-irradiation coupled with weekly thymus irradiation. Various immune challenges were then introduced and examined. After the study, the results from the immune-depleted rabbits were compared to those from non-irradiated rabbits. Key findings involved identifying where in the lymph node the response to both thymus-dependent and thymus-independent plasma cells were initiated, as well as distinguishing two unique precursors to antibody-forming B-cells.

Creating a T-cell Deprived Model

• The researchers induced a state of T-cell deficiency in rabbits using two doses of sublethal total body X-irradiation, supplemented by weekly local irradiation of the thymus. This protocol essentially created a ‘clean slate’ with regard to T-cell immunity in the rabbits.

Inducing and Analyzing Humoral Immunity Reactions

• The researchers introduced several antigens and infectious materials to stimulate humoral immunity reactions. These challenges included Salmonella Java vaccine, horse spleen ferritin, horse-gamma-globulin, a chemical sensitizer known as oxazolone, and skin allografting.
• The responses in the draining lymph nodes to these challenges were analyzed both histologically (examining the microscopic anatomy of cells and tissues) and at the submicroscopic level.

Comparing Immune Response in Normal and Immune-Depleted Rabbits

• The immune responses of the T-cell depleted rabbits were compared with similar challenges in non-irradiated, normal rabbits. This allowed the researchers to gauge the effect of the T-cell depletion on the responses.

Site of Initiation of Plasma Cell Response

• The researchers identified where in the lymph node the thymus-dependent and thymus-independent plasma cell responses began. Plasma cells are produced in response to pathogens and are pivotal in producing antibodies to fight infections.

Identification of Antibody-forming Precursors

• The ultrastructural features of the precursors to the antibody-producing B-cells, or marginal zone cells, were described. This enhances our understanding of the early stages of antibody production.
• The researchers also identified and presented two different plasma cell lines that could be recognized at the submicroscopic level.