Immune response restoration with macrophage culture supernatants

Depression of the in vitro immune response of mouse spleen cell suspensions to sheep erythrocytes by removal of macrophages can be reversed by the addition of supernatants from peritoneal macrophage cultures. Supernatant activity can be absorbed by the red cell antigen, and supernatant-treated red cells are stimulatory in the absence of macrophages or supernatant.

Peritoneal macrophages in the immune response to SRBC in vitro

The role of macrophages in the immune response against SRBC in spleen cell suspension cultures obtained from mice was studied.

1. The presence of macrophages increases the number of PFC against SRBC in spleen cell cultures.

2. The ratio peritoneal exudate cells to spleen cells is very critical. Two × 10⁵ peritoneal exudate cells preincubated with sheep red blood cells stimulate 1 × 10⁷ mouse spleen cells to an optimal response. This reaction is suppressed when 2 × 10⁶ peritoneal cells are used.

3. Spleen cell populations which had lost the capability of producing antibodies by elimination of cells adhering to glass yielded a strong immune response upon addition of 2 × 10⁵ peritoneal exudate cells. The significance of macrophages for the induction of the immune response is discussed.

Vulcanizate Structure, Relaxation, and Tensile Strength of Polyisoprenes

The tensile strength of lightly-filled sulfur vulcanizates of 1,4-cis polyisoprene is lower the more the specimen has undergone deformation after removal of a definite stress. With equal tensile strength, this deformation multiplied by the modulus is proportional to the square of the filler concentration. Along with this deformation the volume of the elongated specimen increases through the formation of internal stress cracks. Rupture originates even at lower stresses in the neighborhood of the filler particles. It is affected by the size of the filler particles as well as by the chemical nature of the filler and by the structure of the network. Encouraged by these results we checked the network structure. We examined the stresses at high elongations, the photoelaetic homogeneity and the turbidities and viscosities of solutions of the degraded vulcanizates, and found small local variations in crosslink density and differences in the number of elastically-ineffective chain ends. The number of these chain ends and the local variations of crosslink density may increase greatly during vulcanization, and substantially reduce the tensile strength.