Cellular Differentiation of the Immune System of Mice

Plaque forming cells (PFC) of different immunoglobulin classes producing antibodies against sheep erythrocytes were separated according to their buoyant densities by means of equilibrium centrifugation in a stepwise BSA gradient. In the period of 7–10 days after immunization γM PFC are markedly enriched in fractions of low density and relatively depleted in fractions of high density. The distribution of total γG PFC shows less enrichment in the lower density fractions and less depletion in the higher density fractions. The density profile for γG2a PFC is even flatter, with a significant difference (depletion) relative to the unseparated spleen cells only in the highest density fraction. The density gradient distributions of cells able to transfer an adoptive immune response of the various immunoglobulin classes are markedly different from the PFC distribution. Cells obtained 7–10 days after immunization able to transfer an IgM response are present in the same proportions across the density gradient, whereas memory cells for γG2a obtained at this time are markedly enriched in fractions of low density and virtually depleted from high density fractions. With increasing time after primary immunization, the γG2a memory cells increase progressively in density and by 6 weeks the higher and lower density fractions have the same proportions of γG2a memory cells. The total γG (mainly γG1) memory cells by 7–10 days show slight enrichment in low density fractions and no depletion in high density fractions. The conclusions were reached that (a) memory for γG1 develops earlier than memory for γG2a and (b) that memory for anti-SRBC antibodies of different classes is carried in separate cells. When gradient fractions enriched for PFC and memory cells for all classes were completely depleted of PFC using glass bead columns, the ability of this fraction to transfer memory for all classes was not diminished. This shows that memory cells are not identical with cells secreting antibodies.

Section: Discussionsupporting

confidence: 83%

Immunological Memory in Mice

L’age-Stehr

Herzenberg

1970

“…Class restriction of marrow cells and of the units of response to antigens of SRBC (ASU) has been discussed elsewhere (25). A critique of the limiting dilution approach has also been given in publications of this series.…”

Section: Discussionmentioning

confidence: 99%

Cellular Differentiation of the Immune System of Mice

Cudkowicz

Shearer

Ito

1970

Self Cite

Marrow cells and 5 x 107 thymocytes of unprimed (C57BL/6 x DBA/2)F1, (C57BL/10 x WB)F1 and (C3H x C57BL)F1 donor mice were mixed in vitro and transplanted into X-irradiated syngeneic hosts. Upon injection of sheep erythrocytes, splenic plaque-forming cells (PFC) secreting IgM (direct PFC or IgG (indirect PFC) hemolytic antibody were enumerated at the time of peak responses. By grading the numbers of marrow cells, inocula were found that contained few immunocompetent cells reaching the recipient spleens, interacting with thymocytes or other accessory cells (or both), and generating PFC. The frequency of responses in BDF1 mice conformed to Poisson statistics, indicating that immunocompetent marrow cells participated in a single-hit interaction limiting PFC responses. The marrow cells assayed were not restricted for the antibody class (IgM versus IgG) to be secreted by mature PFC. Unrestricted marrow cells could have been either the precursors of PFC or accessory cells. Different results were obtained in BWF1 and C3BF1 mice. The frequency of responses in relation to the number of marrow cells grafted did not follow Poisson statistics, and the limiting cells were restricted for antibody class. Presumably, immunocompetent cells of these strains were more heterogeneous than those of BDF1 mice and participated in a multiplicity of cell-to-cell interactions. The strain differences reflected inherent properties of marrow cells and not influences of the environment in which PFC were produced. The results confirmed for bone marrow the heterogeneity of immunocompetent cells reported by others for spleen, and suggested that genetic factors such as "immune response" genes regulate cellular differentiation also for functions other than those related to antibody specificity.

“…Assays for Immunocytes and for Hemolytic FooL--The procedures for enumerating plaqueforming cells (direct and indirect) and clnster-forming cells have already been described (3,13,14). The assays were performed on spleen cell suspensions of individual mice in duplicate or triplicate.…”

Section: Methodsmentioning

confidence: 99%

“…Splenic ASU of unprimed and primed mice are committed to the exclusive production of one of the following types of immunocytes: direct hemolytic plaque-forming cells (PFC), indirect hemolytic PFC, and hemagglutinating cluster-forming cells (CFC) (3,13). Thus, splenic ASU engaged in anti-SRBC responses are rather specialized or differentiated cells of the immune system.…”

Section: Marrow-thymus Antigen-sensitive Iyn[tsmentioning

confidence: 99%

Cellular Differentiation of the Immune System of Mice

Shearer

Cudkowicz

1969

Self Cite

The immune response to sheep erythrocytes (SRBC) is initiated in mice by functionally distinct cells not directly engaged in sp~.Sfic antibody production. These ceils are either capable of reacting with antigens or of generating mature immunocytes by interactions, proliferation, and differentiation. They constitute a functional unit called antigen-sensitive unit (ASU), detectable by transplantation bioassays