Long-lasting rat growth enhancement by an immunoregulating synthetic peptide

We have studied the long-lasting effects on rat weight gain of an active immunization with a peptide construction consisting of the covalent linkage of the 104-113 GH sequence to the 323-339 sequence of ovalbumin and to adjuvant muramyl dipeptide (MDP). The 104-113 GH sequence has already been identified as a potential epitope capable of enhancing growth hormome (GH) activity when complexed with the specific antibodies. Our results show that: a) 104-113 peptide antibodies after reacting with the endogenous GH produced a weight gain up to 7% higher than that observed in unimmunized rats; and b) the position of the adjuvant sequence in the molecule was critical for the immune response. Antibodies elicited in hypophysectomised rats had no effect on weight gain, thus confirming that the increase in hormonal activity is actually linked to the binding of specific peptide antibodies to endogenous GH.

Two monoclonal antibodies identify antigens preferentially expressed on normal human breast cells versus breast cancer cells

In order to obtain antibodies with specificity toward normal mammary epithelial antigenic determinants, we immunized BALB/c mice with normal milk cells and screened the hybridomas against an undifferentiated breast cancer cell line H466B, peripheral blood lymphocytes and normal fibroblasts. Two hybridomas were generated, which produced BA6 (IgG1) and CA4 (IgM) monoclonal antibodies (MAbs). These MAbs did not react with 5 breast cancer cell lines. In cryostat sections of normal human breast tissue, BA6 was reactive with 6/6 and CA4 was reactive with 12/13 specimens both showing an apical staining of epithelial cells. Conversely staining of malignant cells in breast cancer biopsies was observed in 4/33 specimens with BA6 and in 4/19 specimens with CA4. Computerized image analysis (SAMBA) of immunostained sections showed homogeneous distribution of staining, with a high percentage of stained cell surfaces in normal breast (mean percentages of positive surfaces : BA6 : 75% and CA4 : 82%) while, in malignant samples, staining was heterogeneous, with a mean percentage of positive surface of 25% for BA6 and 12% for CA4. Both MAbs reacted strongly with human milk fat globule membranes (HMFGM) and skimmed milk. FPLC size exclusion chromatography of skimmed milk showed that CA4 and BA6 reactive materials eluted in distinct peaks in high molecular weight ranges. Electrophoretic separation of HMFGM followed by CA4 staining detected a high molecular weight reactive band (Mr 380-600 kDa). CA4 and BA6 reactivity was reduced by protease treatment of the antigen but was not affected by neuraminidase digestion, by methanol extraction or by Na-metaperiodate oxidation. After perchloric acid treatment of HMFGM, BA6 activity was lost while the CA4 activity was found in the soluble fraction. The results reported suggest that the two MAbs identify two distinct novel epitopes of normal breast cells.