The Nature of MHC Restrictions in T-B Cooperation

The I region of the mouse major histocompatibility complex plays an important role in controlling the interactions between T helper cells and B cells in response to antigen. For example, MHC incompatible T cells from BALB/c mice cooperate well with BALB/c B cells but poorly with CBA B cells in antibody formation. Data will be presented on helper T cell function in the PFC response to TNP-KLH in four sorts of mice, namely: a) double bone marrow chimeras (e.g. C3H + BALB/c stem cells → irradiated (C3H × BALB/c) F1 recipients), b) single chimeras (e.g. C3H or BALB/c stem cells into (C3H × BALB/c) F1 recipients), c) F1 → Parental chimeras (e.g. (C3H × BALB/c) F1 stem cells into C3H or BALB/c recipients), d) CBA mice rendered neonatally tolerant to BALB/c spleen cells.

These studies suggest that the following factors determine optimal interaction between MHC incompatible T and B cells.

Immunosuppressive activity of carrageenan for cell-mediated responses in the mouse

Unfractionated carrageenan was highly toxic to CBA mice. By using moderately nontoxic regimens, the immunosuppressive properties of carrageenan were examined in several assays. The growth of tumour allografts was only modestly enhanced at low dosages, but dramatic enhance ment of tumour growth and feeble prolongation of skip allograft survival occurred only at a very high dose. Mixed lymphocyte culture reactivity was significantly diminished at both high and low doses. Phytohaemagglutinin responsiveness was suppressed in the spleen but not in the mesenteric lymph node cells. Changes in the ability of normal syngeneic lymphoid cells to "home" to the lymphoid organs of treated mice were confined to the period immediately after carrageenan administration, an observation that was not temporally related to the suppressive action of carrageenan. It is concluded that, compared with its effect on antibody formation, carrageenan is a very poor inhibitor of cell-mediated responses. Possible reasons for this are discussed.

Cell-mediated immunological responsiveness in mice decomplemented with cobra venom factor

In vivo administration of cobra factor (CoF) the C3-activating protein of cobra venom, had no suppressive effect on the in vitro response of lymphocytes to PHA, LPS or allogeneic cells; nor did it affect the generation of cells cytotoxic to allogeneic target cells. HVG reactivity was inhibited by commercially available but not purified CoF, and the latter also failed to prolong skin allograft survival. It is concluded that in vivo complement depletion does not interfere with T cell responses, and that previous reports of prolonged survival of skin allografts and inhibition of cutaneous delayed hypersensitivity reactions following treatment with CoF may have been due to impurities in the preparations used.

A quantitative study of smooth muscle cells in reflux, obstructed, and triad bladders. A preliminary report;

This quantitative study has shown that the average size of the vesical smooth muscle cells of humans increases with age, whereas the average nuclear size remains constant. In the bladders of six babies with proven outflow obstruction, the cell size was signigicantly increased. In 23 of 25 bladders of infants and children with vesicoureteral reflux there was no apparent hypertrophy, but in two the cells were larger than normal and the micturition cystourethrograms exhibited features which may signify impairment of outflow. In two autopsy bladder specimens of two newborn, triad syndrome babies, there was no hypertrophy of muscle cells, indicating absence of obstruction in fetal life. Three giant bladders associated with rectovesical fistula deformities (two newborn specimens) and dyskinesia of the small and large bowel showed no hypertrophy of muscle cells, indicating that the enlargement was unlikely to be obstructive and appeared to be developmental in origin. Hypertrophy of muscle cells of the bladder indicated obstruction to the outflow, even when the degree of obstruction was mild. Muscle cell size can be measured on full thickness small surgical biopsy specimens prepared as paraffin sections and hence the method can be useful in clinical practice.

The response of smooth muscle cells in the rabbit urinary bladder to outflow obstruction

The morphologic response of smooth muscle cells in the urinary bladder to a standardized bladder neck obstruction and the cell changes subsequent to release of that obstruction were studied in both growing and adult rabbits. The bladder reacted first by gross dilation and then by concentric thickening of the wall at the expense of the lumen. Microscopically, thickening of the bladder wall was due to temporary submucosal edema, then to the increased fibrocollagenous connective tissue, and finally to the increased muscle mass which in part replaced the connective tissue. Hypertrophy of the smooth muscle cells and their nuclei was apparent and this preceded cellular hyperplasia, which did not occur until 30 days after the obstruction was induced in the adult rabbits. In contrast, there was early hyperplasia of smooth muscle cells in the growing rabbits, followed by hypertrophy of the cells and their nuclei. In no instance could mitosis of smooth muscle cells be found in either young or adult rabbits. Quantitation showed that the degree of cellular hypertrophy was proportional to the duration of the obstruction. In the adult animal, the muscular thickening was mainly due to an initial 5 fold increase of the muscle cell volume together with a later 3 fold increase of muscle cell number. In the growing rabbits, the muscle cells first doubled in number and then after 8 weeks a 6 fold enlargement of cell volume contributed to the total muscular thickening. Upon release of obstruction in the adult rabbits, both enlarged cell and nuclear sizes regressed to normal values and the cell numbers gradually decreased to near normal values over periods up to 4 months after release.

Specific unresponsiveness to skin allografts in mice. IV. Immunological reactivity of mice treated with liver extracts, Bordetella pertussis, and antilymphocyte serum

The strain-specific unresponsiveness to H-2 incompatible skin allografts induced by treatment of adult mice with single inoculations of donor strain liver extract and Bordetella pertussis vaccine, as well as three doses of antilymphocyte serum, has been investigated by several in vivo and in vitro methods, with a view to elucidating it mechanism. Lymphoid cells from mice with long surviving skin grafts were found to be reactive in graft-versus-host assays (as measured by splenomegaly or popliteal lymph node enlargement), and mixed lymphocyte culture tests gave positive results. Attempts to cause lethal runting of F1 hybrid mice injected at birth with spleen cells from unresponsive mice gave variable results. However, the injection of F1 hybrid cells into the footpads of unresponsive animals failed to elicit a significant host-versus-graft response. Although lymphoid cells from unresponsive animals did not include detectable numbers of cytotoxic cells, such cells could be generated by previous in vitro mixed lymphocyte culture stimulation or, to some degree, by the injection of the animals with F1 hybrid cells. Attempts to prevent mixed lymphocyte culture stimulation or cytotoxicity with serum from unresponsive mice failed at the serum concentrations used. The data indicate that long-term unresponsiveness in this system is maintained by the production in the hosts of factors that interfere with the cell-mediated response.