The role of lysosomes in immune responses

The primary immune response in mice. 3. Retention of sheep red blood cell immunogens by the spleen and liver

The antibody-inducing activities of foreign red blood cell immunogens sequestered in the spleens and livers of mice injected with sheep erythrocytes were evaluated during the early periods of the immune response. Estimates of immunogenicity, obtained from the magnitudes of anti-sheep red blood cell hemolysin responses evoked in sensitized recipient mice by subcellular tissue fractions prepared from these phagocytic organs, showed that the liver and spleen differ greatly in their handling of this particulate antigen. The liver, functioning primarily as a scavenger organ, destroys completely the immunogenicity of the heterologous erythrocytes in 12 hr. In contrast, the spleen handles foreign erythrocyte immunogens in at least two different ways: approximately 90% of the initially sequestered activity is rapidly destroyed by the spleen in 6 hr, but the remaining activity, associated chiefly with a tissue fraction possessing the sedimentation properties of "light mitochondria," is retained at a significant level for 3 days, and then progressively decreases to a low level until the 7th day. A correlation of the observed changes in the properties of the immunogenic tissue fraction with known cellular events in the spleen stimulated by antigens indicates that the retention of the degradable erythrocyte immunogen is essential for stimulating and maintaining immune reactions in this antibody-producing organ.

Potentiation of the T-lymphocyte response to mitogens. II. The cellular source of potentiating mediator(s)

Effective supernatants (SUP), which potentiate mouse T-cell responses to phytohemagglutin (PHA), are obtained from cells of several species (human, rabbit, rat, mouse) and indeed from syngeneic spleen, thymus, or bone marrow cells. Unstimulated cells release some SUP activity but more is produced after stimulation. Lipopolysaccharide (LPS) produced very active SUP in all cultures tested. PHA was similarly active on human leukocytes only, whereas concanavalin A (Con A) gave highly efficient SUP only with mouse spleen cells. SUP production is not correlated with a mitotic response of the donor cells and is observed in cultures unable to respond mitotically to the stimulant. Adherent mouse spleen cell populations, consisting largely or entirely of macrophages, produce active SUP, while nonadherent cells do not. Similarly, purification of human peripheral leukocytes on nylon columns, with removal of macrophages and other adherent cells, destroys their ability to produce SUP. The importance of indirect effects in stimulating mitotic responses of T cells is emphasized by the fact that the mitotic response of mouse thymocytes to LPS and its ability to potentiate the response of these cells to PHA disappears with removal of adherent cells from the thymocyte population. Conversely the production of SUP from spleen cells stimulated by Con A requires the presence of T cells.

Ultrastructural changes in cells of the mouse footpad infected with Mycobacterium leprae

Ultrastructural changes in cells of the mouse footpad are described which occurred during the log phase of multiplication, the plateau, and the stationary phase of growth of Mycobacterium leprae.BALB/c mice were inoculated in the right hind footpad with 5 x 10(3) organisms and sacrificed in pairs at 86 to 173 days after inoculation. Tissue samples were prepared for electron microscopy by standard techniques. During the early growth phase of M. leprae in the mouse footpad, few organisms can be detected. Those present are in macrophages and are bound by a single membrane. The cytoplasm of the macrophage is less dense around the organism. There are few lysosomes, and the bacteria do not appear to be degenerating. At the peak of the growth phase, the organisms within a macrophage are bound by either a single or double membrane. There is an increased number of vacuoles, which are also bound by a double membrane, and lysosomes. During the stationary phase, most of the macrophages have taken on a vacuolar appearance and contain lysosomes. The vacuoles are bound by a double membrane, as are most of the organisms within the macrophage. Many of these organisms appear to be degenerating. Occasionally, organisms are encountered in the sarcoplasm of striated muscle. They are usually bound by a single membrane and do not appear to be degenerating.