In different murine systems, delayed-type
hypersensitivity (DTH) swelling responses at 24-48 hr after
antigen challenge were preceded by an early 2-hr swelling response. The 24-hr DTH response is thought to depend on this early (DTH-initiating)
hypersensitivity response. In this paper we show that in the syngeneic DBA/2-SL2 murine tumour system only an early 2-hr swelling response can be evoked. This early
hypersensitivity response was tumour specific and
serotonin dependent. The early
hypersensitivity response in
contact hypersensitivity has been ascribed to
antigen-specific T-cell factors. To test whether similar
T-cell factors were involved in the early
hypersensitivity response in this syngeneic tumour system, we have transferred lymph node, spleen lymphocytes and serum from immunized mice into naive recipients. The serum was fractionated in two fractions, a 50,000-80,000 MW fraction, and a 120,000-190,000 MW fraction. In recipients of lymphocytes, total serum and the 50,000-80,000 MW fraction of the serum, an early
hypersensitivity response can be evoked. So, these data suggest the involvement of specific
T-cell factors in the development of an early
hypersensitivity response against syngeneic tumour cells. Despite the development of an early (DTH initiating)
hypersensitivity swelling response these immunized animals cannot develop a classical 24-hr swelling response. This absence of the 24-hr response in the presence of the 2-hr response is discussed in relation to the frequently observed immune suppression in tumour-bearing mice.