Abstract: Disclosed are peptides the sequence of which defines an immunodominant epitope from the repetitive immunodominant epitope region of the circumsporozoite (CS) protein of a member of the genus Plasmodium, the sequence of the peptide being shorter in length than the repeating unit of the CS protein.

Abstract: There are disclosed polypeptide compositions having the following amino acid sequence as the active site:ARG-LYS-ASP-VAL-TYRThese polypeptides have the capability of inducing the differentiation of T-lymphocytes but not of complement receptor (CR.sup.+) B-lymphocytes and thus are useful in a number of therapeutic areas. Also provided are derivatives of the pentapeptide, novel intermediate polypeptides, methods of manufacture of the peptides, therapeutic compositions, and methods for use of the compositions.

Abstract: There are disclosed new polypeptide compositions having the following amino acid sequence as the active site:TYR-ASN-ILE-GLN-LYSThis polypeptide has the capability of inducing the differentiation of both T-precursor cells as measured by the acquisition of the thymic differentiation antigens TL and THY-1 (.theta.), as well as B-precursor cells as measured by the acquisition of receptors for complement, a distinctive marker of B cells. The peptide is thus useful in thymic function and immunity areas such as in treatment for a congenital absence of thymus. The peptide is active in very low concentrations. Also provided are derivatives of the pentapeptide, novel intermediate polypeptides, methods of manufacture of the peptides, therapeutic compositions, and methods for use of the compositions.

Abstract: There are disclosed new polypeptide compositions having the following amino acid sequence as the active site:TYR-ASN-ILE-GLN-LYSThis polypeptide has the capability of inducing the differentiation of both T-precursor cells as measured by the acquisition of the thymic differentiation antigens TL and THY-1 (.theta.), as well as B-precursor cells as measured by the acquisition of receptors for complement, a distinctive marker of B cells. The peptide is thus useful in thymic function and immunity areas such as in treatment for a congenital absence of thymus. The peptide is active in very low concentrations. Also provided are derivatives of the pentapeptide, novel intermediate polypeptides, methods of manufacture of the peptides, therapeutic compositions, and methods for use of the compositions.

Abstract: There are disclosed polypeptide compositions having the following amino acid sequence as the active site:ARG-LYS-ASP-VAL-TYRThese polypeptides have the capability of inducing the differentiation of T-lymphocytes but not of complement receptor (CR.sup.+) B-lymphocytes and thus are useful in a number of therapeutic areas. Also provided are derivatives of the pentapeptide, novel intermediate polypeptides, methods of manufacture of the peptides, therapeutic compositions, and methods for use of the compositions.

Abstract: There is disclosed a tridecapeptide of the following sequence:H.sub.2 N--Gly--Glu--Gln--Arg--Lys--Asp--Val--Tyr--Val--Gln--Leu--Tyr--Leu--COOHthis tridecapeptide has the capability of including the differentiation of T lymphocytes but not of complement receptor (CR.sup.+) B lymphocytes and thus is useful in a number of therapeutic areas. Also provided are novel intermediate polypeptides and methods of manufacture of the peptides.