Monoclonal antibody against human CD4, said antibody presenting a dissociation constant (KD) less than 1 x 10-9 M, binds to an extracellular region of human CD4, and is: (i) a recombinant human hybrid antibody in which the heavy chain variable region (VH) of the antibody comprises the amino acid sequence of SEQ ID NO: 12 but which excludes the secretory signal sequence of amino acids 1 to 19 in SEQ ID NO: 12, and the light chain variable region (VL ) of the antibody comprises the amino acid sequence of SEQ ID NO: 22 but which excludes the amino acid secretory signal sequence 1 to 20 in SEQ ID NO: 22； or (ii) a recombinant humanized antibody in which: (a) the VH of the antibody comprises the amino acid sequence of SEQ ID NO: 96 and the VL of the antibody comprises the amino acid sequence of SEQ ID NO: 78； (b) the VH of the antibody comprises the amino acid sequence of SEQ ID NO: 98 and the VL of the antibody comprises the amino acid sequence of SEQ ID NO: 78； (c) the VH of the antibody comprises the amino acid sequence of SEQ ID NO: 77 and the VL of the antibody comprises the amino acid sequence of SEQ ID NO: 78； (d) the VH of the antibody comprises the amino acid sequence of SEQ ID NO: 100 and the VL of the antibody comprises the amino acid sequence of SEQ ID NO: 78； or (e) the VH of the antibody comprises the amino acid sequence of SEQ ID NO: 100 and the VL of the antibody comprises the amino acid sequence of SEQ ID NO: 102.Anticuerpo monoclonal frente a CD4 humano, presentando dicho anticuerpo una constante de disociación (KD) inferior a 1 x 10-9 M, se une a una región extracelular de CD4 humano, y es: (i) un anticuerpo híbrido humano recombinante en el que la región variable de cadena pesada (VH) del anticuerpo comprende la secuencia de aminoácidos de SEC ID nº: 12 pero que excluye la secuencia señal secretora de aminoácidos 1 a 19 en SEC ID nº: 12, y la región variable de cadena ligera (VL) del anticuerpo comprende la secuencia de aminoácidos de SEC ID nº: 22 pe
